jditlfm

Hello I thought maybe you guys could shed some light on a problem me and my girlfriends father have been having with his vette. It is a 1989 Vette with tune port and has 36k on it. The car wont start when its warmed up, maybe in closed loop?, the injectors wont open because when he cranks you cant feel the tick if you hold your finger on them, I will fire if you spray staring fluid down the intake but wont run. The fuel pressure is good because we confirmed it with the gauge. If you let the car cool back down it will fire right back up and run until you shut it off, but wont start back up. Also sometimes the car surges a little and I found if you unplugged the tps sensor it smoothed right out, I don’t know if that’s related.

So I guess my question is what is causing the injectors to work during starting when its warmed up? Thanks

vader86

Anytime the car starts its in open loop until its timers expire.

What does the fuel pressure do immediately after shutdown, does it hold steady and for how long, or does it immediately drop?

whitez52

Have you tested for leaking injectors,regulator and fuel pump.

RRT vette

Try the suggestion Vader86 made. Also use an ohm meter and check ohms of the injectors hot and cold. The should be around 16 +/- one or two. You have to remove the pigtails connectors to access the injector terminals.

AGENT 86

I'll throw "ignition module" into the mix. Without a reference signal from dist, the ECM will not fire the injectors. From what iv'e read, it's somewhat common for the module to fail when it gets too hot and once cool, it begins to work properly again.

Sam Lam

The injectors are suspect.....just as RRT Vette stated. The resistance of the injectors can change....if the coils are shorting out. That year of car seems to have a high injector failure due to the design of the part. I use 16 to 17 ohms as a spec. Anything less than 16 is shorting out. This is an easy test.

RRT vette

Steps are taken to troubleshoot these things. I first start with any codes stored. Next is fuel tests and try to rule it out. Then I test for spark. Air is usually the last I check but not the least important.

jditlfm

The fuel pump is definitly not the problem as well as leaking injectors or the regulator. The PSI Held steady when the car was shut off and would spike to 40 PSI if you unpluged the vacuum to the regulator. For some reason the injectors just dont fire when the car is hot. You can drive the car anyware and it will run fine but as soon as you shut it off you have to wait till its cold again to restart it. I am going to cheack the ohms on the injectors but how would i test the ignition modual, an olliscope? Thanks for the help guys

RRT vette

The ignition module can be tested at Autozone...make sure they do a 10 cycle test to insure it gets hot. The DRP's are sent to the ECM and then to the injectors. From your last post I think the igniton module would be the next step.

tjwong

The easiest thing to do to make sure that the ignition system is working. Just pull a easy vacuum hose off the plenum, then take carb cleaner like Berrymans or CRC, spray a good dose into the plenum. If the ignition system is OK, then the engine will fire up when you crank if over. If it doesn't then the reason that you don't feel the injectors pulsing is because the ECM isn't firing them, and that means its not getting reference pulses from the Distributor. Which can be caused by, a bad ICM or a bad pick up coil in the distributor. Either peice can cause it. If she fires up, then I would be doing a resistance test on all the injectors after the problem rears up. Electrical devices can often fail when hot, and resistance values change with temperature. Test them immediately after the car fails to start.

FF1wms

i have an 89 and had this exact problem. after many frustrating hours and some parts replacing, i got around to replacing the ignition modual. that was it. it was alot cheaper than i thought it would be. i think around 30.00. : i should have done that earlier, but i had spark ,so i went looking elsewhere. turns out the spark kept getting weaker until it wouldn't fire anymore. even then still had visual spark. i would give this a try. i started looking toward a fuel problem. and that could get real expensive, fast. good luck. good call 86

FF1wms

by the way i did also find a bad injector and a couple starting to go bad. unfortunatly it didn't cure the starting problem, but finding this i prevented another problem. thanks to samlam.
thanks bob.

jditlfm

So I replaced the pickup coil and the ignition module with no success. I finally as a last resort measured the resistance of the injectors and got readings of 3.5 ohms on 1 and 10 ohms on about 6 other ones and 16 ohms on about 2 injectors. This has to be a problem correct. I just wanted to run that by you guys before I went out and bought injectors. Thanks for all the help.

RRT vette

Yes, they are the problem. I would replace all 8.

Sam Lam

I agree with RTVette! You have a bad case of Multec disease. You can replace the injecctors without pulling the runners from the intake. If you want info on this, send me a note. Suggest you replace the injecectors with 22# parts. Do not drive the car with shorted injectors

zr1fred

I just had a similar problem with my 89. When I shut it off and immediately tried to start it, it would just crank. Let it sit for three or four minutes, it would start. Had one bad injector , replaced it same problem. It turned out to be bad injectors. I changed everything before I found the problem. The difference is it would run if you primed it. I have had intermitant problems with the TPS causing no start problems, and you can't start it by priming it.

Sam Lam

Warning to 89 to 91 Vette owners as part of this thread! Here is a note from Rich Jensen, Cruzin Performance on injector problems with 89, 90 and 91 Vetts:

Hi Bob,

The problem you currently have is that from 1989 through 1991 on the L98 engines GM installed Multec injectors. These injectors have one of the highest failure rates of any injector ever installed. It's not a matter of "if" they are going to fail, it's simply a matter of "when" they will fail. That is why some of your injectors look differently than the others. Some of them have obviously already failed and were replaced. Because of their design they cannot be repaired so the only solution is to replace them.

You can try to find some of the same injectors to use as replacements however they will likely eventually fail also so a better alternative is to replace them with an aftermarket set of replacement injectors or find some of the earlier Rochester injectors that were used from 1986 though 1988 on the L98's. These were a Bosch design injector and they don't have the problems that the Multecs do.

I don't sell any injectors so I can't help with supplying replacements but if you do find a set of the earlier design injectors I can service those and they have a very good track record of long life and serviceability. The part numbers you would be looking for are: 1986 = 5235211, 1987 and 1988 = 5235302. These are the part numbers that are on the injectors themselves. They are not the part numbers that would be listed in a GM parts catalog.

Sorry to be the bearer of bad news but that's just the way the Multec injectors are.
Hope this helps. Let me know if you need more info or have additional questions.

Rich Jensen

I hope this info helps other people with similiar problems.

jditlfm

So what lbs hour should i look into. I was looking at these
http://store.summitracing.com/partde...5&autoview=sku
I am not worried about ever upgrading the car it will stay stock as long as he owns it. Thanks guys you are the best.

jditlfm

ttt....

stubbs

I upgraded my setup to 30lbers, but the info I received seemed accurate across the board on any # injector being............use Ford MotorSport injectors, they are a direct swap and are the best dollar to quality value in Bosch style injectors out there, they work great, and all 8 of my Red top 30#'s were about 205 dollars from Summit.