Just finished installing a set of Bosch III's (pictures and small write-up within)
07-26-2009, 05:53 PM
#1
Racer
Thread Starter
Just finished installing a set of Bosch III's (pictures and small write-up within)
Just though I'd post up some pic's I took last night during a fuel injector swap on my '92 Corvette. These injectors are the Bosch III design sold as a replacement set of injectors for the '86-'92 L98/LT1 equipped car's. I purchased them through one of our sponsors (Fuel Injector Connection) last week and they arrived just in time for me to install them over the weekend.
I figured I'd write up a little "how-to" about the install on an LT1 in case any of you had plans of one day doing the job yourselves. The entire process really only requires about 20 minutes of actual work. Some may want to take a bit more time like I did to clean up the fuel rails like I did and snap off a few photo's but all in all, this job can be done in no time.
I went with the Bosch III's because they come highly recommended by many members right here on Corvette Forum. I've read nothing but good comments about the Bosch's performance as well as Jon over at FIC for his great customer service.
A little background:
About 5-6 weeks back, my car began having a slight stumble at part throttle acceleration each morning after I'd start the car to go to work. The car would start up easily enough, but before I'd get 2 blocks from my house, there was a bit of hesitation around 1800-2000rpm. It would only last for a few seconds and then clear itself out and the car would run fine afterwords. The strange part was, if I drove the car hard for those first first minute or two of driving, the "hesitation" issue wouldn't occur at all.
As time went on, it got to the point where this would no longer happen just in the morning, but every time the car would sit for more than an hour or two. There was also a slight "choppyness" to the idle which didn't sound right even though the tach itself showed a pretty steady idle. The past 2 weeks, the car also started using up a lot more gas than usual.
After doing a little research here on CF, I found others who had experienced similar issues with their cars. As it turned out, many times the cause of these drivability issues were due to the factory Mutec injector's (which apparently were never that good to begin with) wearing out.
At only $169 for a full set of 8 over at F.I.C. - the Bosch III's were a no brainer. Even if my Multec's weren't my problem, they're still 17 years old and they'd eventually start giving me problems anyway so I figured why not? I also decided to replace the fuel filter as well just to be safe, so I ordered a stock replacement filter from Napa.
Here are the Bosch III's right out of the box as shipped from F.I.C.
I first removed the gas cap to release any built-up pressure and disconnected the battery. After removing the fuel rail covers, I started off by removing the locking clips that secure the plugs to the injectors. Each injector has one locking clip for a total 8 clips all together. Then I removed the 4 bolts that secure the fuel rail in place with a 10mm socket and finally removed the small vacuum hose connecting the fuel pressure regulator to the intake manifold on the passenger side.
..
Very carefully, I pried up on the fuel rail's one side at a time to pull the injectors out of the bungs on the intake manifold and gently flipped the fuel rail backwards towards the windshield leaving the injectors pointing upwards. (At this point, you're going to want to slide a tray or lay down an old rag underneath the fuel rails for the next step as there will be some fuel leakage from the fuel rail after removing the injectors)
Before you can remove the injectors from the fuel rail, you're going to have to remove the locking clips that are holding them in place. I used a small flat head screwdriver to carefully pry and slide them out. (The newer style Bosch III's don't require the use of these clips anymore so you won't be needing them any longer)
Keep in mind that there will still be some pressure left inside the fuel rail, so when you take out the first injector, be sure to have a rag underneath it to catch/absorb and fuel spray that may occur. Once you've removed all eight injectors, remember, if you're going to turn the fuel rail over to clean/polish it up before it goes back on, keep a rag/tray underneath it to catch whatever fuel that's still inside the rail. There's not a lot, but you don't want to get any fuel accidentally falling into any electrical connections. - Better safe then sorry...
..
These are the old Multec's that you'll be taking out and a shot of them side by side with the new Bosh III's:
..
Here's are some shots of the a new Bosch III injector and the old Multec for comparison. You can clearly see from these photo's that the Bosch's are a lot thinner in shape than the old Multec's and weigh only about half as much as well.
..
..
Because the Bosch III's are factory replacements, their connection is identical to the Multec's:
..
Bosch III spray nozzle compared to the Multec:
..
Side by side comparison from both ends of the injectors:
..
***************
After taking some comparison photo's of both injectors, I got back to work. The Bosh's III's come with new o-rings already on the injector. I used a bit of dielectric grease around the rings on both intake and fuel rail sides of each injector to help them slide into place. You're going to want to place the injectors in the intake manifold side first by gently rocking them side to side until they slide into place. DONT try and "twist" them into place!
..
The new injectors are in place on the intake manifold side:
..
I figured I'd write up a little "how-to" about the install on an LT1 in case any of you had plans of one day doing the job yourselves. The entire process really only requires about 20 minutes of actual work. Some may want to take a bit more time like I did to clean up the fuel rails like I did and snap off a few photo's but all in all, this job can be done in no time.
I went with the Bosch III's because they come highly recommended by many members right here on Corvette Forum. I've read nothing but good comments about the Bosch's performance as well as Jon over at FIC for his great customer service.
A little background:
About 5-6 weeks back, my car began having a slight stumble at part throttle acceleration each morning after I'd start the car to go to work. The car would start up easily enough, but before I'd get 2 blocks from my house, there was a bit of hesitation around 1800-2000rpm. It would only last for a few seconds and then clear itself out and the car would run fine afterwords. The strange part was, if I drove the car hard for those first first minute or two of driving, the "hesitation" issue wouldn't occur at all.
As time went on, it got to the point where this would no longer happen just in the morning, but every time the car would sit for more than an hour or two. There was also a slight "choppyness" to the idle which didn't sound right even though the tach itself showed a pretty steady idle. The past 2 weeks, the car also started using up a lot more gas than usual.
After doing a little research here on CF, I found others who had experienced similar issues with their cars. As it turned out, many times the cause of these drivability issues were due to the factory Mutec injector's (which apparently were never that good to begin with) wearing out.
At only $169 for a full set of 8 over at F.I.C. - the Bosch III's were a no brainer. Even if my Multec's weren't my problem, they're still 17 years old and they'd eventually start giving me problems anyway so I figured why not? I also decided to replace the fuel filter as well just to be safe, so I ordered a stock replacement filter from Napa.
Here are the Bosch III's right out of the box as shipped from F.I.C.
I first removed the gas cap to release any built-up pressure and disconnected the battery. After removing the fuel rail covers, I started off by removing the locking clips that secure the plugs to the injectors. Each injector has one locking clip for a total 8 clips all together. Then I removed the 4 bolts that secure the fuel rail in place with a 10mm socket and finally removed the small vacuum hose connecting the fuel pressure regulator to the intake manifold on the passenger side.
..Very carefully, I pried up on the fuel rail's one side at a time to pull the injectors out of the bungs on the intake manifold and gently flipped the fuel rail backwards towards the windshield leaving the injectors pointing upwards. (At this point, you're going to want to slide a tray or lay down an old rag underneath the fuel rails for the next step as there will be some fuel leakage from the fuel rail after removing the injectors)
Before you can remove the injectors from the fuel rail, you're going to have to remove the locking clips that are holding them in place. I used a small flat head screwdriver to carefully pry and slide them out. (The newer style Bosch III's don't require the use of these clips anymore so you won't be needing them any longer)
Keep in mind that there will still be some pressure left inside the fuel rail, so when you take out the first injector, be sure to have a rag underneath it to catch/absorb and fuel spray that may occur. Once you've removed all eight injectors, remember, if you're going to turn the fuel rail over to clean/polish it up before it goes back on, keep a rag/tray underneath it to catch whatever fuel that's still inside the rail. There's not a lot, but you don't want to get any fuel accidentally falling into any electrical connections. - Better safe then sorry...
..These are the old Multec's that you'll be taking out and a shot of them side by side with the new Bosh III's:
..Here's are some shots of the a new Bosch III injector and the old Multec for comparison. You can clearly see from these photo's that the Bosch's are a lot thinner in shape than the old Multec's and weigh only about half as much as well.
....Because the Bosch III's are factory replacements, their connection is identical to the Multec's:
..Bosch III spray nozzle compared to the Multec:
..Side by side comparison from both ends of the injectors:
..***************
After taking some comparison photo's of both injectors, I got back to work. The Bosh's III's come with new o-rings already on the injector. I used a bit of dielectric grease around the rings on both intake and fuel rail sides of each injector to help them slide into place. You're going to want to place the injectors in the intake manifold side first by gently rocking them side to side until they slide into place. DONT try and "twist" them into place!
..The new injectors are in place on the intake manifold side:
..
Last edited by LT1*C4; 09-04-2011 at 10:02 PM.
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gman35 (02-22-2019)
07-26-2009, 05:53 PM
#2
Racer
Thread Starter
With the injectors in place, you're going to flip the fuel back over and "GENTLY" position it so that the top of each injector fit's snug within the bungs of the fuel rail. Once all eight are in place, install the 4 bolts back into place and tighten them by hand. Be sure to continuosly check all eight injectors to make sure they're going in straight as your tightening, otherwise you'll run the risk of damaging one if it's not lined up with the fuel rail properly. This is why you tighten them by hand first.
I started with the front two bolts and worked my way back. Once I had tightened the bolts as much as I could by hand, and confirmed that all eight had seated properly within the fuel rail, I tightened them the rest of the way with a socket wrench. Remember, the intake manifold is aluminum, as is the fuel rail. You don't have to torque the bolts down too hard otherwise you'll dent the fuel rail or even worse, strip the screw threads in the manifold opening. Just tighten everything nice and snug.
Finally, plug each injector plug back in to their respective injector and reinstall the holding clips. They simply slide right into place with a push of your finger and lock the plug firmly into place. Next, remember to attach the small vacuum line back into the fuel pressure regulator and intake manifold.
..
That's about it as far as installing the fuel injectors. At this point, you can throw the fuel rail covers back on and reconnect the battery...
..
Now, unless you've changed out your fuel filter recently, odd's are you're going to want to replace it the same time you do your fuel injector swap. There's not much point in buying and installing new injectors only to foul them up after a couple month's because your filter is allowing contaminants to pass through.
I picked up a replacement fuel filter from Napa. Cost was only about $10 but in my case, it was definitely worth it. I didn't take any photo's of the install because there's not that much to photograph. The filter is located on the passenger side just to the right of the exhaust manifold. Because I have headers on my car, I had more clearance to work with but it was still a bit of a pain. You'll need both a 13/16 and a 5/8 wrench to loosen the fittings. Again, be careful when prying the hard line out of the filter as there is still some pressure left in the line. Be sure to have a bucket or pail underneath the filter. You way also want to wear a set of safety glasses just to be safe. Gasoline really stings if it lands in your eyes. Ask me how I know...
..
Taking the new filter out of its box, I held it to my lips and blew into the end of it. It required no effort at all and I could feel my breath passing through to the other end of the filter.
After removing the old filter and trying the same, I was amazed that I had to blow into the end of it as hard as I could, just to feel ANY air passing through it.
This was obviously the original 17 year old filter and it showed. I was surprised the car was even able to run at all. Just for the hell of it, I decided to cut the filter open to see its condition. You can see from these pictures that the pleats have basically turned into stiff pieces of cardboard. I tried to spread them apart and they literally started to crumble in my hands
Anyways, by now your injectors should be installed, as well as your new fuel filter. Double check to make sure all the fittings/plugs/connections/vacuum line are all attached and secure and if you haven't already done so, re-connect the battery. Before you attempt to start the car, you're going to have to prime the fuel system. Simply turn the key to the "start" position and wait for the fuel pump to come on. Wait until it stops, then turn the key off.
Wait a few seconds and repeat the process. Do this about 4-5 times to build pressure in the fuel system and then start the car. It may take 2-3 cranks but it will turn over. Once again, inspect the injectors and fuel lines for any leaks. If you're satisfied all is well, take your Vette out for a spin and put some miles on her. The ECM was erased when you disconnected the battery so you're going to have to drive the car around for a while for the computer to basically "re-learn" everything over again so give it a bit of time.
CONCLUSION:
Well, after taking the car out last night and putting some miles on her, I'm happy to say that the car does in fact feel better than before. How much of this has to do with the fact that the car's got new injectors or the fact that I replaced the fowled up fuel filter remains to be seen. According to my tach, my idle was pretty solid before I started this project, but like I said, it just didn't "sound" right and I'd hear an occasional "sputter" from the exhaust every now and then while it idle. That "sputtering" sound is now gone. The car's throttle response seems more responsive then before and the just feels a lot smoother during acceleration at wide open throttle.
I haven't driven the car long enough since yesterday to comment on whether my fuel consumption has increased/decreased since the swap, but I'll be sure to update this post after I put some more miles on the car.
Anyways, hope this post helps some of you. The job isn't very difficult at all and can easily be accomplished by someone with basic hand tools and is not afraid to get their hands dirty. All in all. A worth wile upgrade.
Big thanks to Jon at Fuel Injector Connection, Corvette Forum and the members who helped me in the right direction.
Thanks again to everyone!
I started with the front two bolts and worked my way back. Once I had tightened the bolts as much as I could by hand, and confirmed that all eight had seated properly within the fuel rail, I tightened them the rest of the way with a socket wrench. Remember, the intake manifold is aluminum, as is the fuel rail. You don't have to torque the bolts down too hard otherwise you'll dent the fuel rail or even worse, strip the screw threads in the manifold opening. Just tighten everything nice and snug.
Finally, plug each injector plug back in to their respective injector and reinstall the holding clips. They simply slide right into place with a push of your finger and lock the plug firmly into place. Next, remember to attach the small vacuum line back into the fuel pressure regulator and intake manifold.
..That's about it as far as installing the fuel injectors. At this point, you can throw the fuel rail covers back on and reconnect the battery...
..Now, unless you've changed out your fuel filter recently, odd's are you're going to want to replace it the same time you do your fuel injector swap. There's not much point in buying and installing new injectors only to foul them up after a couple month's because your filter is allowing contaminants to pass through.
I picked up a replacement fuel filter from Napa. Cost was only about $10 but in my case, it was definitely worth it. I didn't take any photo's of the install because there's not that much to photograph. The filter is located on the passenger side just to the right of the exhaust manifold. Because I have headers on my car, I had more clearance to work with but it was still a bit of a pain. You'll need both a 13/16 and a 5/8 wrench to loosen the fittings. Again, be careful when prying the hard line out of the filter as there is still some pressure left in the line. Be sure to have a bucket or pail underneath the filter. You way also want to wear a set of safety glasses just to be safe. Gasoline really stings if it lands in your eyes. Ask me how I know...
..Taking the new filter out of its box, I held it to my lips and blew into the end of it. It required no effort at all and I could feel my breath passing through to the other end of the filter.
After removing the old filter and trying the same, I was amazed that I had to blow into the end of it as hard as I could, just to feel ANY air passing through it.
This was obviously the original 17 year old filter and it showed. I was surprised the car was even able to run at all. Just for the hell of it, I decided to cut the filter open to see its condition. You can see from these pictures that the pleats have basically turned into stiff pieces of cardboard. I tried to spread them apart and they literally started to crumble in my hands
Anyways, by now your injectors should be installed, as well as your new fuel filter. Double check to make sure all the fittings/plugs/connections/vacuum line are all attached and secure and if you haven't already done so, re-connect the battery. Before you attempt to start the car, you're going to have to prime the fuel system. Simply turn the key to the "start" position and wait for the fuel pump to come on. Wait until it stops, then turn the key off.
Wait a few seconds and repeat the process. Do this about 4-5 times to build pressure in the fuel system and then start the car. It may take 2-3 cranks but it will turn over. Once again, inspect the injectors and fuel lines for any leaks. If you're satisfied all is well, take your Vette out for a spin and put some miles on her. The ECM was erased when you disconnected the battery so you're going to have to drive the car around for a while for the computer to basically "re-learn" everything over again so give it a bit of time.
CONCLUSION:
Well, after taking the car out last night and putting some miles on her, I'm happy to say that the car does in fact feel better than before. How much of this has to do with the fact that the car's got new injectors or the fact that I replaced the fowled up fuel filter remains to be seen. According to my tach, my idle was pretty solid before I started this project, but like I said, it just didn't "sound" right and I'd hear an occasional "sputter" from the exhaust every now and then while it idle. That "sputtering" sound is now gone. The car's throttle response seems more responsive then before and the just feels a lot smoother during acceleration at wide open throttle.
I haven't driven the car long enough since yesterday to comment on whether my fuel consumption has increased/decreased since the swap, but I'll be sure to update this post after I put some more miles on the car.
Anyways, hope this post helps some of you. The job isn't very difficult at all and can easily be accomplished by someone with basic hand tools and is not afraid to get their hands dirty. All in all. A worth wile upgrade.
Big thanks to Jon at Fuel Injector Connection, Corvette Forum and the members who helped me in the right direction.
Thanks again to everyone!
Last edited by LT1*C4; 08-08-2009 at 05:27 PM.
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gman35 (02-22-2019)
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gman35 (02-22-2019)
07-27-2009, 07:25 AM
#9
Drifting
Great write-up! Glad to see you picked the right vendor and the right product.
One suggestion: I would leave the fuel rail covers OFF until starting and running the engine. In this way, ANY fuel leak would be very obvious and could be corrected immediately.
SAVE the WAVE!
One suggestion: I would leave the fuel rail covers OFF until starting and running the engine. In this way, ANY fuel leak would be very obvious and could be corrected immediately.
SAVE the WAVE!
07-27-2009, 08:53 PM
#12
Thank you very much for the write up. Having just changed my fuel filter today, here's a tip. The gas never stops dripping from the fuel line into the filter. I kept waiting and waiting and it never stopped. In the end I looked for something to plug the line with and it just so happens that there's a blue plastic plug on one end of the Napa gold fuel filter when you buy it. You can use that plastic cap to cap the fuel line so no more gas comes out. Whether it was made for that or not I'll never know but it fits perfectly.
Oh yeah, I laughed about the gas stinging the eyes and thought to myself, "How hard can it be to look away when undoing the line". Well you're right, gas does sting in the eye.
Oh yeah, I laughed about the gas stinging the eyes and thought to myself, "How hard can it be to look away when undoing the line". Well you're right, gas does sting in the eye.
Last edited by -=Tom=-; 07-27-2009 at 08:55 PM.
04-25-2010, 03:37 PM
#13
4th Gear
Member Since: Nov 2007
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Bosch injector install
Just finished installing the Bosch IIIs on my 92 LT1. Took care of a cold start flooding problem caused by injectors leaking into the intake manifold for any down time over about 1 hours. Original injectors with 118 K miles.
The writeup was great and much better than similar writeups in various manuals. I didn't tackle the fuel filter yet since I was a bt short of time, but it is next.
A suggestion. To relieve fuel line pressure and burn off some fuel in the rails before removing them and injectors, just pull the fuel pump fuse and run the car til it runs out of pressure at the rails. Takes less that a minute.
The writeup was great and much better than similar writeups in various manuals. I didn't tackle the fuel filter yet since I was a bt short of time, but it is next.
A suggestion. To relieve fuel line pressure and burn off some fuel in the rails before removing them and injectors, just pull the fuel pump fuse and run the car til it runs out of pressure at the rails. Takes less that a minute.
04-25-2010, 04:01 PM
#16
Le Mans Master
and Jon is a class act. Nice write up 
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gman35 (02-22-2019)
04-25-2010, 06:13 PM
#19
Race Director
04-25-2010, 06:51 PM
#20
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Member Since: Mar 2010
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Yes, very nice write-up indeed! The only problem is that I found this forum AFTER I bought my Accel 24lb'ers for my '91 coupé. It was still a little less than $300 for the set which is still a whole lot better than the $200 each my dealer wanted for the OEM injectors. I mean I know GM is in trouble, but c'mon... I don't think I should have to pay off their debt to the government all by myself!
If those Accels ever give up the ghost, I know where my next set of injectors will come from! And with all due respect to Jon, I hope its not for a while!
If those Accels ever give up the ghost, I know where my next set of injectors will come from! And with all due respect to Jon, I hope its not for a while!