I know this is not related to my third generation bird, but maybe someone will have an idea(if it gets locked i understand, if it does you guys can email me at thirdgenbird@hotmail.com, if you have any ideas)

Anyways, I have a 1995 GMC Jimmy for my daily driver. It is a 4.3 liter with CPI. (thank *** not TBI) It just rolled 72,000 miles. It has recently developed a hard start issue. It will always crank like normal. Sometimes it will fire up right away(like normal) others it will fire after about 10 seconds of cranking. It always starts though, and once it is running it runs top notch. I have replaced the fuel pump,filter and fuel pump relay. I hooked up a fuel pressure guage, it reads 58 when i turn the key on, and holds steady when i crank it(these engines need 55 to start) So could itbe my fuel pressure regualtor? Maybe it is leaking making it hard to get fuel to the injectors. But if that was bad why wouldn't it run rough when it was running? If it was the injector i would think it would run rough once it was running. So i bought all my tune up parts last night in hope that it might solve my problem. Any ideas, sorry for posting on this board for a jimmy. The only jimmy board i could find has not responded all week to my question. I think everyone there is dead.

 

Wow, 55 psi to start... wow. The max that an f-body MPFI/TPI pump can put out is 60 PSI!! I wonder if you've got any vacuum leaks or exhaust leaks... did you read the plugs at all to see if one (or a few) are loaded up with deposits?

I forget offhand how to check the regulator; but I know you can do it with the fuel pressure gauge. Pull the vac line off the regulator; if there's fuel in the vacuum line, the regulator's diaphragm is shot.

How's the timing? Ignition system in good shape? It's odd because you'd think a long cranking time means fp relay, but you say you get 58 psi as soon as you turn the key on. If the fp relay was bad, you'd have 0 psi until you cranked the motor enough to get oil pressure (and therefore, fuel pressure).

 

I forgot to tell you tom that it does not do it every time, only when it wants i guess, isn't that strange.

 

Do you think it's temperature related?

 

Nope, it has done it both when the weather cooled off, and when we had that heat rush here in chicago. I also do not believe it is moisture related. It just seems like it works when it wants. If the regulator was leaking, would the truck run normal when driving down the road.

 

Does the motor have the cast iron intake or the plastic composite one?

Since you already replaced the pump, the fuel pressure regulator is most likely your problem. On the CPFI engines, the regulators leak pretty often. Hell, I just did one today on a '98 G-van w/5.7L and I've done a bunch on ******* (astro) Vans.

One thing you can do is put the FP gauge on. Turn the key to ON, then QUICKLY, get underneath the truck and pinch off the rubber part of BOTH fuel lines near the filter. If FP still drops, you've isolated the problem to the engine. Then, it can be 2 things: stuck injector on leaky FP regulator. Since a stuck injector will cause a missfire, you can eliminate that possibility.

 

It would run rich, but the PCM can compensate to an extent. You might notice a difference, and you might not. Depends on how badly it's leaking.

 

Not on these motors, Tom. The regulator is underneath the top half of the intake. The top half has to come off to reach it.

Yep, on the CPFI engines, the injectors aren't solenoids. It's more like 1 injector/brain that distributes fuel to the neccesary cylinder via a hose to the runners. The hoses have poppet valves on the ends that REQUIRE a minimum of 50 psi to open.

 

I think electrical/ignition.
What color is exhaust upon starting?
Black?

 

Actually there is no smoke upon startup. Once it fires it runs normal. But i did have someone checking for smoke. Last night i pulled off the vortec cover,the tuning valve, and looked inside the plenum. On the left side the fuel pressure regulator sits in a cavity. I would assume that should be dry in there. There is not a lot of gas, but enough to lead me to believe that my regulator is leaking. Karl, if it was ignition, what would you check first and how.

 

It shouldn't be wet in there. You found your problem.

 

I once had a bad modular and it caused all sorts of problems for a year. Finally it totally crapped out. I replaced modular & all those problems I chased for a year went away.
Know what?
That was new modular I installed, too!

Glad you found your problem.

I admit I don't know every Fuel Injection detail. Too many differnt "same" systems.
And one day, I'm gonna tackle a 1957-65 Corvette Fuel Injection system, too (for swapping between my 1967 Camaro & 1974 Corvette-I still dream, too!!)!
Problem is I don't have a time machine for those cheap prices!
The new FI from GM engine ones are nice, but... Old Speed parts are SO BITCHIN & ALL REET!

 

There is only a little bit if moisture in there. But i would think it shoudl be bone dry. And if there were any big amount of gas in there, where would it go. Would it evaporate. Or would it build up and i would explode?

Anyways, the new pressure regulator is 95 dollars so i will be buying one unless anyone else thinks this is the wrong diagnosis. I believe cali is right though.

 

"The only jimmy board i could find has not responded all week to my question. I think everyone there is dead. "


Only SOME of us are dead Here!

 

 

The fuel is leaking into the intake manifold. That fuel gets sucked into the cylinders causing an extreme rich condition, aka Flooding.

You'll need the regulator, and 2 seal/gasket kits. If you're willing to wait till monday, i can get GM part numbers for you.

P.S. I coulda swore that regulator was less than $60. Hmmm.

 

I would appreciate the part number, thanks. I am going to buy the regulator monday. I am going to a junk yard today to see if i can find a used one. thanks again

 

Ok, just to make sure what engine you have, is the 8th digit of the VIN a "W" or an "X"?

 

It is a "W", thanks for your help

 

Ok, I got the VIN codes wrong. "W" means you have the cast iron intake. Now i know exactly what motor we're dealing with.

Now, i've got some good news and some bad news. On these engines, the fuel pressure regulator is part of the fuel injectors. You can't buy it separate. The injector assembly is not cheap, although if you wait and order it through www.gmpartsdirect.com you can get it for cost.

Here's the part numbers:
Injector assembly: 17113673
Gasket: 10105939

Now, some possible good news. Here in California, trucks with this engine and RPO YF5 (california emissions package) have a special policy. If the regulator or injectors fail, GM will replace it free, if the vehicle is under 10 yrs/ 100,000 miles. THIS ONLY APPLIES TO CA VEHICLES.

BUT, if I were you, I'd call your local GMC (it has to be GMC, not chevy or pontiac, etc) and ask if there is a special policy concerning the injectors/regulator. Maybe you'll get lucky.