i apparently have a fuel leak down problem, and i believe it to be the injectors, but tell me what you think, or if you know other possibilities that could cause it.

a couple of months ago when i initially attempted turns on my rebuilt engine, i discovered that i had fuel getting in to the crank case. supposedly the pressure that was set at about 48 was too high. here i am now with the engine ready for exhaust, and when i set the fuel pressure up this time, it was 42. talking to my machine shop guys, that's about right. well, i checked one spark plug and found it was wet with fuel, so it's still getting excess somehow. today while i set the timing, etc., i set it to 38 and then shut the engine off and left the gauge on it. in a matter of about 25-30 minutes, pressure dropped to about 24. so even though i had the injectors cleaned and serviced and supposedly all were good, my opinion is that they are leaking, dumping in to the cylinders...

with all that in mind, i am running an LT4 hotcam in it with stock (22#) injectors, and a holley afpr. someone help me out, please... thanks.

KAM

 

First, did you set the fuel pressure with the engine off. GM says about 40-48 psi with key on engine off. Turn on the key and let the 2 sec prime cycle operate, turn off the key and then on again and look for max pressure. Start the engine and you should see about a 3-10 drop at idle. After the engine is off you should see a drop and then it will stay fairly steady. The only way for fuel to get into the engine is probably leaky injectors many times caused by minescule pieces of dirt. Other leakdown causes can be a bad check valve in the fuel pump, line leaks or failure to replace the rail and injector O rings. How does it run? Is it running rich, black smoke from the pipe? Are you letting it come off open loop before checking the plugs? If you have a leak bad enough to get fuel into the crankcase you should see almost an immediate drop to zero within a few minutes. Another way to look at whats going on is to scan the O2 sensor. I have seen intake leaks cause excessive fuel delivery. Get it running and try a can of fuel system cleaner. Get back with more info.

 

iset the initial fuel pressure at 37 with the engine off, then 42 engine running, no vacuum on the regulator. can't tell you about black smoke from the pipes, as i have not been under the car with it running (only headers and tubes on it right now), although it does seem to run well. i had checked the plugs with the engine cold. injectors were cleaned and checked before rebuilding engine, not to say they didn't fail (has happened to me before), or pick up some trash from the residual crap in the tank and lines. all the o-rings were replaced, too. no external leaks anywhere.

i won't be able to get back to it til this weekend, but will look in to all you mentioned. news at 11, as they say.

IF i have to replace the injectors, any recommendations? i've heard accel...

 

A pressure drop of 14 PSIG in 30 minutes should not be that distressing. Chances are that the fuel is leaking back through the pump check valves or FPR and not past an injector. You can test the FPR by keeping the vacuum line disconnected for the test. If fuel appears at the vacuum fitting, the FPR is leaking. I'm guessing that if you pinch the fuel supply line closed after shutting off the engine, pressure will maintain. I could be wrong (again) though.

 

DO A SEARCH --- There are numerous posts about the Holley AFPR (I have one too). Holley says they have a "safety feature" built into them that causes all of them to bleed off the pressure quickly. Not sure how they do it, but every Holley AFPR I've seen and heard about will drop off at least as much as you're talking about in 25 minutes or so.....