Need some ideas
07-04-2013, 07:39 PM
#21
Melting Slicks
This is not a fuel pump problem, it is a tune problem. You need more acceleration fuel. The pressure will drop when you rev the engine in the driverway because your intake vacuum goes up. On the road at wot the vacuum will drop and pressure will go up. You already raised pressure to 70the psi, if the pump was shot that would not happen. One other note doubling fuel pressure only raises output 41%.
07-04-2013, 07:52 PM
#23
Le Mans Master
Thread Starter
Before I just go out & shoot the car I have a question, let's forget all about the hesitation for a minute, if the pump is not weak then why did I have to open the throttle so much to bring the idle up where it is supposed to be? I could raise the idle by adding pressure then I can close the throttle back within the range of the tps. I'm not doubting anyone, I just don't know. I'll be the first to admit I am in way over my head on this. If it weren't for tunedport90 I wouldn't be this far along. Also, I have had sooty tailpipes all through this but when I boosted the pressure the exhaust cleaned up immediately.
Last edited by Midnight 85; 07-04-2013 at 07:55 PM.
07-04-2013, 08:30 PM
#26
Melting Slicks
As I recall you upgraded your ECM. Did you have this problem before you installed the upgrade tune? If not, I suspect the tune rather than the fuel pump. I'm on my third pump. I have never had one kind of fail. They've been more like turning off a switch.
I agree that revving the engine will not increase fuel pressure. You need to put a load on to lower the vacuum. Some data logging would be very helpful.
I agree that revving the engine will not increase fuel pressure. You need to put a load on to lower the vacuum. Some data logging would be very helpful.
07-04-2013, 09:05 PM
#27
Drifting
So what is the consensus on the horsepower capacity of the stock pump? I have heard many stories of the stock pump not up to the task of a modded engine. And fuel pumps have always been weird in every GM car I have owned. I have had several that checked out just fine pressure wise, but a new pump curing whatever symptom I have had at the time, such as hard starting, hesitation, etc.
07-04-2013, 09:29 PM
#28
Le Mans Master
Thread Starter
As I recall you upgraded your ECM. Did you have this problem before you installed the upgrade tune? If not, I suspect the tune rather than the fuel pump. I'm on my third pump. I have never had one kind of fail. They've been more like turning off a switch.
I agree that revving the engine will not increase fuel pressure. You need to put a load on to lower the vacuum. Some data logging would be very helpful.
I agree that revving the engine will not increase fuel pressure. You need to put a load on to lower the vacuum. Some data logging would be very helpful.
07-04-2013, 11:29 PM
#29
Le Mans Master
=)
Try driving it with a FP gauge taped to the WS. No hesitation with the stock tune.. that kinda takes the pump out of the equation but better safe than sorry.
07-05-2013, 12:34 AM
#31
Le Mans Master
Thread Starter
The tune from pcm was set for 30 lb. injectors. I have a pressure gauge on my A pillar and it is dead on. I checked with a regular tester and they read the same. That's how I knew the pressure would climb when accelerating but it had stopped that the last day or so but I thought it might be because I was running so much pressure. With the pressure set at 38 lbs. and the fact that it dropped one lb. when I put the vacuum on the regulator certainly can't be right can it? It should have dropped more than 1 lb. I have already made arrangements for another tune if the pump makes no difference. (Which is probably the case) Normally I don't throw parts at it but from what I read on Google and here I thought it was the pump. I had already ordered it just before cumbercr had said it was the tune, then bjankuski said the same so that's where I am right now, AFU. You younger guys are all way better at this than me, I'm 64 and I don't want to get into doing my own tuning so I have to go through stuff like this to get what I want. I would have thought that pcmforless would have gotten a lot closer with the tune than they did and I realize they could not hit it dead on but that's another story.
Last edited by Midnight 85; 07-05-2013 at 12:37 AM.
07-05-2013, 12:43 AM
#32
Le Mans Master
Thread Starter
Can any of you tell me this, I made no changes at all except putting in the new injectors and setting them at FIC's suggested pressure. Why was the idle so low? I had to open the throttle blade quite a bit to get it to idle at 800 where it is supposed to. By the time I had it set at 800 the tps could not be moved far enough to bring it down even close to .54
07-05-2013, 09:07 AM
#33
Melting Slicks
First, you are not to old to learn a few more tricks. You and I are in the same age range. It is not at all unusual to have a tune that just doesn't work. When I first fired up my 396 it was so rich I was afraid I washed the cylinders.
Some questions: What cam are you running? Do you now have 30# injectors installed? Which tune are you using?
Having the wrong size injectors for the tune will really screw with your mixture. If I understand correctly, PCM tuned for 30# injectors but they were actually 24#? Smaller injectors would of course cause a lean condition across the entire range. You said you then installed a stock memcal and it ran better. The stock tune would have been for 22# injectors so that makes sense.
Increasing fuel pressure to compensate may be OK for troubleshooting purposes. But the solution is to adjust the MAF tables in the tune. To do that you will need to do some data logging. Data logs will reveal where you need to add fuel and where to take away. By the way, I run fuel pressure at 43.5 psi. That way the injectors are working at their rated pressure.
Target idle rpm is part of the tune. Do you know for sure the tune you are using was set for 800 rpm? You should only have to adjust the throttle blade to dial in an IAC count of 45ish at idle.
I believe your problems will go away with the correct tune. I'd give PCM another shot at it. Then provide them with the data logs so they can dial it in. An AFR gauge would be very helpful for adjusting WOT.
Some questions: What cam are you running? Do you now have 30# injectors installed? Which tune are you using?
Having the wrong size injectors for the tune will really screw with your mixture. If I understand correctly, PCM tuned for 30# injectors but they were actually 24#? Smaller injectors would of course cause a lean condition across the entire range. You said you then installed a stock memcal and it ran better. The stock tune would have been for 22# injectors so that makes sense.
Increasing fuel pressure to compensate may be OK for troubleshooting purposes. But the solution is to adjust the MAF tables in the tune. To do that you will need to do some data logging. Data logs will reveal where you need to add fuel and where to take away. By the way, I run fuel pressure at 43.5 psi. That way the injectors are working at their rated pressure.
Target idle rpm is part of the tune. Do you know for sure the tune you are using was set for 800 rpm? You should only have to adjust the throttle blade to dial in an IAC count of 45ish at idle.
I believe your problems will go away with the correct tune. I'd give PCM another shot at it. Then provide them with the data logs so they can dial it in. An AFR gauge would be very helpful for adjusting WOT.
07-05-2013, 10:56 AM
#34
Le Mans Master
Thread Starter
First, you are not to old to learn a few more tricks. You and I are in the same age range. It is not at all unusual to have a tune that just doesn't work. When I first fired up my 396 it was so rich I was afraid I washed the cylinders.
Some questions: What cam are you running? It's a fairly mild Summit brand, I compared specs to a Comp Cam I was looking atDo you now have 30# injectors installed?Yes Which tune are you using? I have had both tunes in the car with very similar results
Having the wrong size injectors for the tune will really screw with your mixture. If I understand correctly, PCM tuned for 30# injectors but they were actually 24#? Smaller injectors would of course cause a lean condition across the entire range. You said you then installed a stock memcal and it ran better. The stock tune would have been for 22# injectors so that makes sense.
Increasing fuel pressure to compensate may be OK for troubleshooting purposes. But the solution is to adjust the MAF tables in the tune. To do that you will need to do some data logging. Data logs will reveal where you need to add fuel and where to take away. By the way, I run fuel pressure at 43.5 psi. That way the injectors are working at their rated pressure. That is the setting I am using on the new injectors
Target idle rpm is part of the tune. Do you know for sure the tune you are using was set for 800 rpm? Yes You should only have to adjust the throttle blade to dial in an IAC count of 45ish at idle. Since I can't get a good solid idle I have yet to set the IAC accurately, see the above post of mine concerning idle setting.
I believe your problems will go away with the correct tune. I'd give PCM another shot at it. Then provide them with the data logs so they can dial it in. An AFR gauge would be very helpful for adjusting WOT.
Some questions: What cam are you running? It's a fairly mild Summit brand, I compared specs to a Comp Cam I was looking atDo you now have 30# injectors installed?Yes Which tune are you using? I have had both tunes in the car with very similar results
Having the wrong size injectors for the tune will really screw with your mixture. If I understand correctly, PCM tuned for 30# injectors but they were actually 24#? Smaller injectors would of course cause a lean condition across the entire range. You said you then installed a stock memcal and it ran better. The stock tune would have been for 22# injectors so that makes sense.
Increasing fuel pressure to compensate may be OK for troubleshooting purposes. But the solution is to adjust the MAF tables in the tune. To do that you will need to do some data logging. Data logs will reveal where you need to add fuel and where to take away. By the way, I run fuel pressure at 43.5 psi. That way the injectors are working at their rated pressure. That is the setting I am using on the new injectors
Target idle rpm is part of the tune. Do you know for sure the tune you are using was set for 800 rpm? Yes You should only have to adjust the throttle blade to dial in an IAC count of 45ish at idle. Since I can't get a good solid idle I have yet to set the IAC accurately, see the above post of mine concerning idle setting.
I believe your problems will go away with the correct tune. I'd give PCM another shot at it. Then provide them with the data logs so they can dial it in. An AFR gauge would be very helpful for adjusting WOT.
07-05-2013, 11:57 AM
#35
Unless someone zero'd out a table. i have yet to see a drop in fuel pressure. From a rev. The pressure should maintain.. try installing your OE tune.. if you still have a hesitation and drop pressure.. its the fuel pump.. as stated above keep your pressure gauge on.. facing the windsheild.. and drive and monitor your pressure.. could be a weak pump
Last edited by THE 383 admiral; 07-05-2013 at 12:06 PM.
07-05-2013, 01:05 PM
#36
Le Mans Master
Thread Starter
It's going to have to wait, I already pulled the pump out of the car and am waiting for the new one. I would expect it maybe Monday. I can understand the no drop in pressure from a rev but why doesn't the pressure climb when I pull the vacuum line off the regulator? It always did before.
I have permanent pressure gauge mounted on my A pillar so monitoring pressure is simple, and this how I know how the gauge reacts to certain things. I feel that if the pump was strong it would not drop a pound or two when I do rev the engine.
I have permanent pressure gauge mounted on my A pillar so monitoring pressure is simple, and this how I know how the gauge reacts to certain things. I feel that if the pump was strong it would not drop a pound or two when I do rev the engine.
07-05-2013, 01:56 PM
#37
Melting Slicks
It's going to have to wait, I already pulled the pump out of the car and am waiting for the new one. I would expect it maybe Monday. I can understand the no drop in pressure from a rev but why doesn't the pressure climb when I pull the vacuum line off the regulator? It always did before.
I have permanent pressure gauge mounted on my A pillar so monitoring pressure is simple, and this how I know how the gauge reacts to certain things. I feel that if the pump was strong it would not drop a pound or two when I do rev the engine.
I have permanent pressure gauge mounted on my A pillar so monitoring pressure is simple, and this how I know how the gauge reacts to certain things. I feel that if the pump was strong it would not drop a pound or two when I do rev the engine.
07-12-2013, 10:13 AM
#40
Le Mans Master
Thread Starter
Finally! Today is the day. The new fuel pump will be here today. I ended up having to order another one because the seller of the first one is,,, well let's just say that dealing with him leaves a lot to be desired. I'm getting my money back from the first pump I ordered but it has delayed things a lot with all the waiting. Once I get the new pump in I will see what things are like & post back this evening with who was right.