Help! Help! No Start Condition - 1989 Vette C4

[dhonick]

Have replaced everything, fuel pump (twice), fuel injectors, fuel relay, fuel pressure diaphram, coil, ignition coil, ECM, Fuel filter, plugs, wires. I put a fuel pressure gauge on the rail, when I start on-off with key goes to 40 lb pressure than drops off in 4-5 seconds. Tested rear pressure gauge and was good and checked out. So I unplugged the injectors and turned the key and the pressure held perfectly with very little loss of fuel pressure. Went down slowly as should be. What is making those injectors release the fuel pressure prematurely when the electrics are plugged into injectors? Faulty ECM? Does an ECM need to be ran through dealer to get to work correctly per key make type 1-10? Thanks ~ Danny

 

[vigman]

Ok here are my thoughts...

1) Do you have spark? If so how do you know? and does the rotor ACTUALLY TURN?

2) How many miles on the engine?

3) Is the spark in time? have you hooked up a timing light and check when the line fires?

Reply back

Vig~

 

[vetteoz]

No Start Condition

Does the engine crank over?
Does it try to run?
Black smoke , backfire , anything?

 

[Schrade]

Good job, testing fuel pressure! Most folks just replace parts blindly, without doing a single test (looks like you did replace a few other parts tho' - did they all test bad?)

Fuel pressure test. Just like putting a bike pump on a bike tire valve.

Go to youtube. Bunch of fuel pressure test vids there.

You need to do a static test, and note bleed-down time. Cold motor. Plug in the guage, turn on the key (not start the car). Note the pressure. Watch and write down how long it takes to drop to 0.

If it drops quickly, pull the vacuum hose off of the fuel pressure regulator, and see if you smell gas STRONGLY.

If so, the diaphragm is ruptured in the FPR, and the gas is gettin' drawn in through that hose. If no smell, the FPR diaphragm spring is weak, and it's not holding pressure (this might have been indicated also by insufficient INITIAL KEY-ON pressure reading).

Any FPR-related problem can be confirmed by clamping gently the fuel line before the FPR. You should get max pressure, and it should stay there, unless fuel gets by the pinch. If the pinch is good, and pressure drops anyway, injectors are leaking, or fuel is getting returned backwards. Black exhaust means leaky injectors. Clear exhaust probably means pump/check valve problems.