My mechanic is stuck!

[mjr45]

OK, I have a 75 280 which has a 79 N47 block with an N42 head which has just been cleaned up with valve job and milling .010 to level it out, new injectors (stock), new fuel line (rubber), new fuel filter, new vacuum lines, new AFM and throttle body boots, new connectors on the entire EFI harness. The engine starts but when accelerator rod is pushed, nothing, no revs, just keeps idling then dies. After it dies it won't start unless the fuel line is pinched off. Fuel pressure is there but not measured, we've checked the thermotine, temp sensor and CSV all checked out. The mechanic and I are kinda at a loss any help will be appreciated. Thanks.:mad:

[Zed Head]

"After it dies it won't start unless the fuel line is pinched off. Fuel pressure is there but not measured, "

Just helping you focus...

[grantf]

Well then measure the fuel pressure.

[Pomorza]

Did you look into the TPS? An check the fuel pressure.

Jan

[mjr45]

Supposed to check the fuel pressure today, but haven't heard yet what is is. The TPS was adjusted according to info from Atlantic Z site. Just trying to get some ideas of what to check next. Thanks for the input.

[mjr45]

The fuel pressure reads 34-36 psi when started but it won't run long enough to get any more readings.

[John Coffey]

Your "mechanic" needs to buy this book and read it:

http://www.amazon.com/Bosch-Fuel-Injection-Engine-Management/dp/0837603005/ref=sr_1_1?ie=UTF8&qid=1333303237&sr=8-1

[mjr45]

I gave him my copy of the Fuel Injection Bible, at this point I'm going to get the car back and either try to resolve it myself or take it to another mechanic. This guy is highly recommended by locals as a great mechanic, but now I'm wondering if its just for oil changes!

I'm thinking the issue has to do with the AFM signal to the fuel pump or the TPS signal, the car starts but won't rev and dies after about a minute which tells me its not getting fuel or to much fuel, but there is no fuel smell and the plugs are dry. The TPS was set with the engine not running so it could be that, it may be set so the pints are not opening with throttle. If the AFM signal doesn't get to the pump after start it could be that, but rather than just guessing, I'll check each item by "the book."

Edited April 1, 2012 by mjr45
new info

[Zed Head]

I wrote the following while you were editing. You can take the hose off of the AFM and hold the flap open while starting to test the cutoff switch.

"In your first post you said it wouldn't start unless the fuel line was pinched, which implies low fuel pressure. But now it will start but won't keep running. How long does it stay running? If it's just a few seconds, then it might be the fuel pump cutoff switch in the AFM. It's bypassed at Start but comes in to play at On."

[mjr45]

Zed it runs for about 30-60 seconds and won't restart immediately unless the fuel hose is pinched. The fact that while it is running it won't rev makes me think its the cutoff switch in the AFM. I'm going to get the car back either today or tomorrow and perform the tests in order from the FSM and the EFI Bible to see if I can resolve the problem. Thanks for the input every idea helps.

[mjr45]

Here's the latest in the saga, I went to pick up my car and the mechanic says "Oh, its running great now!" me "What did you do?" mechanic "Well it seems that the dizzy was off, so when I moved the wires 1 post over it started and runs well." WTF I says, why didn't you fix it correctly? No reason he says it was just easier to do this way. Needless to say I'll never go back there for anything and now have to fix what he screwed up.

[Zed Head]

The symptoms don't really match the solution, but if the timing is correct, you might as well drive it as-is until you have some reason to drop the oil pump. It won't hurt anything, and the odds of breaking something while trying to fix something will be reduced. Hopefully your mechanic set the timing with a light and not by ear when he "fixed" it.