Anyone had this electrical issue before?

[GS70350]

My car when cold starts fine. It has 45 psi fuel pressure with the vacuum line off. It runs and drives fine. When i turn it off at operating temperature it will not start again because the injectors do not fire. There continues to be no signal through the injector harness to the injectors until fuel pressure is lowered to a varying point which seems to be getting lower and lower as time passes. Once the pressure is lowered the car will start again and the pressure can be raised back to 45 psi to drive the car with no trouble until i turn it off again.

This sounds like a resistance issue in the wiring somewhere, or a sensor perhaps that cannot push the load of firing the injectors with the pressure as high as it was.

Im going to swap the crank sensor out since i have one sitting around.

 

[scottyb]

I can't imagine that fuel pressure can have any effect on injector electrical signal. They are entirely independent.

 

[Blazer406]

Are you sure it is a fuel pressure issue? I read many posts that say the cam sensor is needed to start the injector firing sequence, but after startup.... it is not needed to maintain the engine running. If this cam sensor were to fault out.... due to heat.... you might not ever know that there was a problem... until you tried to re-crank while it was hot. The unit may function properly when you crank it cold... fault out at some point.... but continue running.....and then when you shut the motor off and tried to re-crank..... no go......

Just a thought....

HTH

 

[soundguy]

I would have to agree on the sensor. After it heats up, things tend to expand a bit and you may be loosing a connection. The connection is reestablished once things cool down. I'd try replacing the cam sensor and going over the connector very carefully.

 

[GS70350]

Yes im thinking its the sensor as well just wondered what you guys thought. I really thought the fuel pressure deal was some wierd crap. I know that as the fuel pressure increases the resistance accross the injectors increase and they become harder to fire. It just sounds to me like a sensor that cannot make up the connection under the higher load when the engine is hot and the pressure is up but can handle the lower load of less fuel pressure.

I dont know if its running in batch fire mode after it starts, hard to tell, but it has no trouble codes thrown at all which would be the case in a total failure of the cam sensor while driving.

Keep thinking about it till i fix it today or tomorrow. Ill let you all know what the problem was.

Thanks

 

[aminga]

Are you sure it is a fuel pressure issue? I read many posts that say the cam sensor is needed to start the injector firing sequence, but after startup.... it is not needed to maintain the engine running. If this cam sensor were to fault out.... due to heat.... you might not ever know that there was a problem... until you tried to re-crank while it was hot. The unit may function properly when you crank it cold... fault out at some point.... but continue running.....and then when you shut the motor off and tried to re-crank..... no go......

Just a thought....

HTH

Actually if the Cam sensor drops out with the Engine running they it will trigger the SES and you'll get a no restart. But then again that might not happen if the sensor just quits giving a signal.

You want to bring it South of town GS? I have tools and a Service manual

 

[SloGN]

Ecm

What size injectors are they ?

first if you have low impendence inj with a stock ecm that could be part of the problem, With the low impedence inj on a stock ecm it builds up heat really fast on the drivers for the injectors.

Try swapping out the ecm with a known good one and drive the car till it gets good and hot the try to restart it.

 

[BuickMike]

Do you get spark? I'm not sure if the ignition module will cause a problem with the ECM keeping the injectors from firing, but I had the same problem once and it was the ignition module. The car would start and run fine, but if I shut it off at operating temp it would not fire until I let it sit for 30 minutes or so. There was a hairline crack on the circuit board on the ign module that expanded with heat. A service rep for a local Buick dealership pointed it out to me and stated that it was somewhat common. BTW after replacing the module the car felt stronger and picked up 3 tenths.

 

[norbs]

I have been doing tests on modules and the failure rate is about 90%. They are just plain no good. Even new ones i buy are not working 100%. I have gone with the type II ignition and have good luck so far. If you do not buy the aftermarket coils for them or GM D546 coils, You will NOT get big improvement over the type I , but the modules do not fail as much.

 

[GS70350]

Always have spark, good and hot, no issues there.

SloGN, I have msd 50s which are high impedence injectors and work fine with the stock drivers in the ECM. It shouldnt be the cause of the problem, but have you seen this problem occur due to overheating injector drivers? I dont have a spare ecm but ill leave it open as a possibility.

If you want to troubleshoot it Aminga it would be a pleasure to head down that way and meet you sometime. Ive got tools and stuff too but it would be nice to have someone else look at it with me.

I havent put much time into it because ive been rebuilding a 2004R and 350 buick to go in my GS which ill be hopefully finishing up this week. Im just carrying around an allen wrench in my pocket so i can start the Ttype when i take it to pick stuff up. Works every time.

Thanks for your input guys

 

[SloGN]

ecm

well i dunno if it's posiable for 50's to create a problem with the drivers. one thing you might want to check is drive the car around witht he ecm down laying in the floor and monitor how hot the case of it gets if it gets some what hott the could be the root of your problem.