2000 Olds Bravada, Starts fine when cold and runs fine. The issue is after it is driven and shut off and sits for half hour or so, there is no start. Eventually will start but takes alot of tries. Will start ok if restarted within 5 or 10 minutes. Hooked up a fuel gauge, Pressurizes to only 53 or so, and around 50 when running( this is before I replaced a partially restricted fuel filter, forgot to check after that) Passes the leakdown test. When pressure manually released to 10, also passes that test(no leak down). When the no starting issue occurs, this is after the pressure has leaked down quite a bit(to like 25 or 30) and won't instantly pressurize to at least 50 to allow it to start. Multiple turning on and off with the key sometimes gets the pressure back up but not always. Once it does start and I shut it off, it will start fine if started within 5 or 10 minutes.

Injectors converted to MFI within the past 25,000 miles, has been running and starting great until now. I also swapped the fuel pump relay with the fog light relay, but that didn't help. Fuel pump has been replaced at least twice in the past 5 years, could it be going bad again? I believe there is an AC/Delco in there now.

108,000 miles on vehicle


Thank for any help!

 

Ok, I checked the pressure with the clean fuel filter. Same as before, 52-54 pressurized, 50 running. Am I correct to state that the MFI conversion doesn't need as high a pressure as the original poppets?(62 psi?). And is the current 8-10 psi difference a sign that the pump is failing and after a heat soak period is causing it to falter? Maybe once it does start again the running fuel cools the pumps internals and will start fine until the next heat soak period. I'm just thinking out loud here.

Runs and starts fine with the current pressure except for the times as stated in my original post.

 

Running pressure is irrelevant.. except you dont have enough difference to account for intake vacuum.
Check with prime, engine NOT running. and see how long it takes for pressure to leak down.

Next time this happens, try pushing accel to floor and hold it there just after you start cranking. That will cut back fuel delivery and if it starts better, you have a leak in the plenum.

Otherwise rig your fuel Pres gage to hook up to the filter input line which allows you to test only fuel pump pressure and leakdown w/o the regulator in the circuit.. should be well over 70, iirc.

I suspect the regulator but would not swear to it. STILL could be FP.

 

Thanks pettyfog. I already checked the leakdown from prime and it seemed to be within the parameters according to the fuel diagnostic section on this forum. I will do the plenum check next time I get a chance and figure out a "T" connection on the inlet side of the fuel filter. I did hold the pedal to the floor a couple of times to clear out the cylinders thinking that an injector was leaking, but I didn't release right after starting to crank.

Edit, as luck would have it, it appears that the kit my pressure tester came with seems to have a "T" fitting for the filter inlet side!

 

Pettyfog, to clarify the plenum leak test: crank and then press accelerator while cranking, or press accelerator, crank, and then release accelerator while cranking?

 

Ok, FINALLY got a chance to test the pressure at the fuel filter inlet. Only pressurizes to 46 psi or so. Even with that, it is sometimes slow getting there. It eventually gets up to 50 after starting and running for a few minutes. Passes the leakdown test allright though.

 

Key on, engine off, fuel pump running: fuel pressure at the service port by the distributor must be 60psi to 66psi. It must remain above 55psi for 10 minutes after the pump shuts off. Your reading of 53psi is far too low.

When checking maximum pump output pressure, don't "T" the pressure tester inline. The fuel line, (at the fuel filter) from the pump must "dead end" at the tester. Pressure while the pump is running should be 78psi to 108psi. If key on, engine off, and maximum pressures are not within specs, check for battery voltage and ground at the pump. If voltage and ground are ok, replace the fuel pump.

The fuel injectors on your Bravada will not squirt fuel if pressure is less than ~43psi.

 

Make sure you start at the basics first. Go through and check the ignition system, and make sure you coil is firing properly and check the distibutor and components( DISTR. TEETH, GEAR, CAP , AND ROTOR) Make sure all spark plug wire are properly routed. Many of ignition component can be checked using an auto multimeter. go over fuel system checks to pinpoint the intermittent problem. These things are usually simple and can easily be overlooked

 

I think Cap'n's on target again. Given car seems to run okay, once started, the only reasons for a slow pressure build but good leakdown, with a dead end test is either very worn pump or low voltage at pump.

Welcome aboard Vortech Chevy Rider... Why dont you actually read the thread before you offer your expertise.
What you wrote here has nothing to do with the problem. It obviously is not ignition and is well on the way to being solved.

BEtter yet post in new member and tell us about yourself and your ride.
And dont get all hurty.. this aint facebook either.. we actually solve problems and fix things here.

 

Captain Hook, I didn't realize that the gauge needed to "dead end" at the inlet hookup. That will need to be another day.