guys, I have a 95 blazer that I've been having trouble with for the last few months. it started with a leeking fuelpressure regulator, changed that and a few weeks later it was bad again (the head popped offf of one of the hold down screws). so then I changed the whole spider assembly, while I had the top of the engine apart I figured it would be a good time for a tune up, so it got new plugs, wires, cap and rotor as well as a whole new distributor. the thing ran fine for a few weeks, then it started with a hard start condition the thing just cranks and cranks and won't start, but once it did it ran fine no engine codes or any other problems. so about a week or so ago it quit while driving, it was sputtering and backfiring, and generally acting like it was starving for fuel. so today I put a new fuel pump in but it still won't start. oh yeah, I have also put a new ignition switch in, in hope that it was that instead of the fuel pump. so it has spark and good fuel pressure but still won't start. any ideas? about the only thing left to change is the computor?

 

Two things that seem to come up a lot on this forum. First, though you say you have good fuel pressure, did you do a fuel leakdown test? Also, from what I have learned on here, if you are not using AC Delco secondary ignition parts...Blazers seem to not run well for long with anything else.

 

i had that issue on my jimmy. it drove me crazy for months. sometimes it would stall on me out in the woods wheeling and id hav to drag it home. ive checked everything on it and then i finally came across the problem. it was an intermitten voltage loss going into the ecm. i forget what wire it was, but i ended up doing a quick temporary fix. cut the wire and tapped up out of the way. then ran a new wire straight from the battery (with an in-line fuse) to the ecm. starts and runs with no problems now. hope this helps.

 

guys, after a few weather and shipping delays I have replaced the fuel pump and lines. I tried to start the truck but it wouldn't a fuel pressure check showed 60 psi key on engine off, and 90+ while cranking. so I replaced the new fuel presuure regulator again and this time got the truck to start and run for a few minutes but the fuel pressure is still crazy high. I totally lost on this one any ideas?

 

90psi at the service port is a problem. If the fuel pressure regulator is exposed to anything above ~75psi, it will rupture the diaphragm.

When you initially turn the ignition to the RUN position, (don't start the engine) the fuel pump should activate for ~2 seconds and then deactivate. The 2 second time frame, (while the pump is activated), is when fuel pressure must be tested. Check fuel pressure and leakdown using this method: Key in RUN position, engine OFF, fuel pump running, pressure must be 55psi to 61psi. It must remain above 50psi for at least 10 minutes after the pump deactivates. Post your results.

EDIT: The excessive fuel pressure problem needs to be repaired first. As long as it remains high, it will continue to destroy regulators.

 

i agree with Captain Hook. 90 psi is way too high. it seems to me like you keep replacing good parts just to find the same problem. i would check the wiring at the pcm for a voltage loss, ground loss, etc.

 

Hey Captain, I thought the psi needed to be 60-66psi with pump running, then above 55psi for ten minutes? Is a '95 different?

 

Yup, 95 and older "W" engines have CMFI. It has one injector that is batch fired. It squirts fuel to all cylinders simultaneously each time any cylinder fires, (3 times per crankshaft revolution). Fuel pressure and leakdown specs are higher on 96 & newer CSFI systems because each injector is only fired once every two crankshaft revolutions. Their reason for increasing pressure is that CSFI injectors have a greater chance of plugging up from not squirting as often.

 

I knew the fuel pressure was a big problem, I just don't get how it gets that High isn't that what the regulator is for? and someone mentioned a bad ground on the PCM, but doesn't the fuel pump get a constant voltage and if there is a bad ground wouldn't that just cause a low voltage condition and thus a low fuel pressure condition? or do they really vary the voltage to the pump?

 

90+ psi for regulated pressure indicates a restriction in the return fuel line, (or a bad regulator). The regulator will not allow pressure to exceed 55psi to 61psi. Anything above regulated pressure gets sent back to the tank through the return line. However, if the return line is restricted, kinked, or the return line was mistakenly connected to the vapor connection on the fuel pump module, pressure will build and indicate maximum pump output pressure, which is around 90psi for your 1995 fuel pump. Locate & repair the restriction, then check regulated pressure again to make sure the regulator is OK.