How do you know if a fuel pres reg is bad?

Ok, you may have read the thread I posted 2 days ago with rough idle, hesitation probs. Well, I took my truck to the Chevy dealer today for a diagnosis. They said it is the fuel pressure regulator. I asked if they were sure it wasn't the fuel pump and they said, and I quote, "Well, we would have to start with the fuel pressure regulator and go from there." I declined having them do the work as I can do either one myself.

Once I got home I started wondering how they arrived at their conclusion. Did they even hook up a fuel pressure guage? So I called back down and asked them that very question. The guy I spoke with said one of their best techs worked on my truck and although he didn't know exactly what he did on it if he says is the pres reg then he was confident he is right. Hmmm...

So, I pop off the reg (which takes like 3 mins) and inspect. This is on a 95 TBI so it's the spring loaded diaphram deal. I pulled the canister off that houses the spring and diaphram and took a look. No signs of wear or anything abnormal looking. I cleaned it all up, put it back together, and put it back on the truck. I started the truck up and let it run for a while. Still the same probs. I pulled the reg off again and looked for any signs of gas leaking through the diaphram. Nothing.

So, here are my questions (finally). How does a regulator go bad? I mean what does it do? I would think the only way for it to go bad is for the diaphram to leak or the pin to not make a seal. It seems to be a pretty simple part really. I, however, have no experience here.

So the bottom line is do I go with the diagnosis of the super tech at the Chevy dealership and replace the regulator? Or do I go with my gut and go straight to the fuel pump? All I'm really trying to do here is save a little money and pick the right one first. I know it's one of the two. The regulator is $95 and the fuel pump is $50. I have both sitting on my counter right now. I just know how ticked I'm gonna be if I throw that regulator on and it isn't the problem and I just wasted $95. The flip side is I'll feel the same if I go for the pump and it isn't the problem because I should have listened to the tech. What do you guys think? I'm going for one of 'em tomorrow afternoon. Any advice?

:banghead:
The answer is - you really dont.
Let me first start by saying that I am NOT a big fan of dealerships. Local ones here in NY are up in the $90/Hr range for repairs, and these guys only have the advantage of RESOURCES. Plus, repairs are a dealers main source of income.
With that said, I will now hop the fence:screwy:
That mechanic might have seen the very problem you have brought him before, and he already has a good idea that the regulator is it. He may know that that particular regulator was faulty, and the part was superceded. He may have checked the running fuel pressure in the line prior to the regulator, and determined that there could be nothing else wrong.
He might also have guessed. This is sometimes not an exact science. Unfortunately, cars are really not built to be worked on these days - they are built to be disposed of.
I would bet that if you can hear the fuel pump running, it is the regulator, and here is why: TBI systems run a similar pressure to a Carb - about 7psi. They are not as sensitive as a 40 - 60 psi MPI system, and the regulator is less complex. The spring in your regulator might have lost its strength, and that is not obvious to your eye.
I will ALSO tell you I am a big fan of proper diagnosis the FIRST time - but it is not always possible. Replace the regulator first, because it is more easily accessable and it is more likely the issue. Dont go too bonkers if it turns out to be something else.
Good Luck!
George
REBEL Motorsports

you might want to check something else, i had the exact same probem on my blazer (5.7 tbi) i also thought is was fuel related, boy was i far off. i took it to a good friend of mine who has his own shop and he specializes in GM's. all i had to do was "tell" him what was wrong, he opened the hood and disconnected the vacuum line from the egr. problem gone. he explained to me that the egr was opening up too early and was basically bogging out the engine giving the symtoms of a fuel problem. changed the egr and the truck never ran so good. on all of the tbi engines i had(7) i never replaced the regulator, i did replace 1 injector for a leak(dumping fuel). good luck.

If you don't want to spend $95 on a reguator at the dealer, go to the local parts store and ask for either the regulator kit or the tbi rebuild kit. Thre regulator kit comes with the gasket for the cap, a new diaphram and spring, the tbi kit comes with that plus all gaskets, o-rings, and injector screens. You can pickup the rebuild kit for about $50, I think the fpr kit runs about $25. Hope this helps.

I had a Fuel regulator go out on my 00Silverado. my symptoms were it would have a hard time starting when it was warm. not sure if that is a symptom you are having.

Dr Olds....you the man! After months of hesitation, just pulling the vacuum hose from the EGR on my '93 K1500 5.7 solved it! and this was AFTER I had replaced the EGR, the plugs and wires, the distributer cap & rotor, the fuel filter, the temperature sensor, the PVC valve, the oil and air filters, the vacuum hoses, etc. None of this did anything until I read your advice.

Now, what to do? The check engine light lights up on the highway. Should I fix something else to make it right or just get used to it? I've had the truck since new and have maintained it myself (no dealer touches it) with a lot of TLC and want to keep it running (and looking) like new.

Dr Olds....you the man! After months of hesitation, just pulling the vacuum hose from the EGR on my '93 K1500 5.7 solved it! and this was AFTER I had replaced the EGR, the plugs and wires, the distributer cap & rotor, the fuel filter, the temperature sensor, the PVC valve, the oil and air filters, the vacuum hoses, etc. None of this did anything until I read your advice.

Now, what to do? The check engine light lights up on the highway. Should I fix something else to make it right or just get used to it? I've had the truck since new and have maintained it myself (no dealer touches it) with a lot of TLC and want to keep it running (and looking) like new.

If you left the vacuume line off of the egr valve it will throw a code and it is hard on the engine. If pulling the line fixed your problem then you need to replace the egr control solenoid.

studentjm,:banhim:

I have a survey for you to take. No surveyor website necessary...
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studentjm

Spammer die will you... :gives:

FishinGuide, I don't know if you've solved your problem or not, yet. I'm going thru a similar problem and am currently running with my EGR bypassed. I can tell you from over a couple of years worth of chasing this damn thing that it is probably not as simple as the EGR solenoid. You should test the solenoid before replacing it, even though it is only $15 to $20. I have a friend that is a mechanic and he's been as frustrated about this problem as me. He had been working on a guy's truck for quite some time with the same issue. He finally discovered that the fuel pressure regulator had a broken spring. The spring does not have to be broken to be bad. Bypassing the EGR only covers up the problem and it will more than likely get worse. You only need to replace the spring, not the whole regulator like a lot of books will tell you. While you're in there, you will probably want to replace the diaphragm and gaskets. The kit is about $25. I'm not sure if that includes the spring or not (I'm going to buy mine this week). You can supposedly buy just the spring, but you may want to have the old one with you when you go. Apparently, it's not "cut and dry" on which one is needed. There are several potential reasons why the EGR bypassing is helping. One of those reasons is the fuel pressure regulator is weak. Another could be the EGR solenoid (simplest). The ECM could be telling a perfectly good solenoid to open too soon. Some other sensor could be telling the ECM that the conditions are right for opening the EGR solenoid (like TPS). What I found today is that the solenoid actually opens up at lower speeds than I originally thought, but I'm being told that is normal. If I hear back from you, I will let you know if my efforts pay off this weekend. Good luck with yours.

as far as i know i have never seen a egr solenoid on any of my tbi's, the vacuum line for the egr went right to the throttle body. from working in various parts depts. and being a tech, if you are using an aftermarket egr(standard, borg warner etc...) there are little shims or washers that you have to put under the valve around the main port of the egr. this gives the a/m egr able to fit many different vehicles. if you do not put these shims under the valve basically you accomplished nothing by replacing it. it has to be shimmed. there should have been a small pkg of them in the box with the egr. i have even seen some of the OEM egr's coming with them because GM is trying to condense the part #'s as they get older. the computer should have no effect on the egr unless you do have a solenoid but that still should have no effect on it on the tbi trucks, on the vortecs it does. if you disconnected the egr and the vehicle runs better than it is an egr problem or egr system problem. you might also want to check that the egr does not have full vacuum that will also cause a problem you want the egr to go to a ported hole on the tbi. check to make supe the vacuum lines are in the right ports.

as far as i know i have never seen a egr solenoid on any of my tbi's, the vacuum line for the egr went right to the throttle body. from working in various parts depts. and being a tech, if you are using an aftermarket egr(standard, borg warner etc...) there are little shims or washers that you have to put under the valve around the main port of the egr. this gives the a/m egr able to fit many different vehicles. if you do not put these shims under the valve basically you accomplished nothing by replacing it. it has to be shimmed. there should have been a small pkg of them in the box with the egr. i have even seen some of the OEM egr's coming with them because GM is trying to condense the part #'s as they get older. the computer should have no effect on the egr unless you do have a solenoid but that still should have no effect on it on the tbi trucks, on the vortecs it does. if you disconnected the egr and the vehicle runs better than it is an egr problem or egr system problem. you might also want to check that the egr does not have full vacuum that will also cause a problem you want the egr to go to a ported hole on the tbi. check to make supe the vacuum lines are in the right ports.

If you have not seen one then you are not looking hard enough or in the wrong place. I have a '94 K1500 5.7L and it has a egr control solenoid, it is about 4 inches from the egr valve, my friends '90 was the exact same way. It is on the right bank, bolts to the spark control module braket.

The 88-95 Chevys that have tbi have egr solenoids like Horse says. They are controlled by the ECM. Vacuum is constantly applied to one side, but the EGR valve only opens when the ECM actuates the solenoid. I did end up replacing the EGR valve last summer, even though I was pretty sure it wasn't the problem. My truck is old, so it couldn't hurt. It came with a gasket, no shims. It looked virtually identical to the OEM valve. I matched the a/m to the OEM p/n on the valve. I'll be tackling the fuel pressure regulator, as soon as my spring arrives. I will be replacing the diaphragm and other tbi gaskets while I'm in there. The mechanic that has been trying to help me just did this to a truck that was having the same symptoms. It fixed it. I've seen this EGR bypassing on several internet sites, but nobody has offered an actual solution. I hope this works on mine.