Is this fuel pressure regulator???

sassee · #1 03-27-2005, 02:23 PM

I have a '97 GMC Suburban (I know this is Chevy forum, no Suburban forum under GMC!) It has a 7.4 in it. A few times lately the truck would not start when hot. Left it for a while, and then it started fine. It's been taking longer to crank than "normal" when cold. Not in minutes mind you, just a little longer. A couple days ago, I was driving it and it acted like it wanted to die a couple times. It was sudden and only lasted fore a second before it was running fine. Yesterday, this happened and it actually did die. I coasted over to side of road, put it in park and luckily, it cranked right back up. Now this blasted thing has had 4 fuel pumps in it, (155000 miles) but I don't think a fuel pump dies and will then restart later. At least the other four never did!!!

Now with gas at $2.00 plus per gallon, I did do a complete tune up, thinking the dist. cap and wires were culprit. Hey it runs great, when it runs! Last night, it would not crank when hot, luckily we had gotten back in from out of town. I put the fuel pressure gauge on and no readable pressure. There was a little bit dribbling from the pressure release, but not enough to run. I did replace the fuel filter. Is this a pressure regulator issue? Or maybe something else???

sassee · #2 03-28-2005, 10:54 AM

Uh....................anybody home????

Larry Derouin · #3 03-28-2005, 11:06 AM

The lack of pressure residual when the key is off sounds more like the check valve at the fuel pump has gone bad. The pressure regulator could very well be marginal BUT, with the symptoms you're describing I'd look at the pump and check valve 1st.

Put the gauge on the fuel line port and check the pressure with the key off. Then turn the key on for 5 seconds (have another pair of hands do this while you watch the gauge). If the pressure comes up fast and stays up, the valve is ok. If it comes up slow and stays up the valve is leaking, and if it doesn't come up(goes to 10 or so and drops right back down) but you hear the pump run, you need a new pump.

The valve IS NOT a separate item, but is integral to the pump. It's just a rubber flapper valve that can get dirt and grit on it's seat and then leak.

If and when you take the tank out have it steam cleaned. This should help keep the dirt down. Also change gas stations to one that has a lot of business. This keeps fresh gas in his underground tanks, and minimizes the probability of dirt and water in the gas.

Larry

GunnerinTX · #4 03-29-2005, 03:41 PM

I have a similar problem with my 99 5.7 and 94k miles. I took it to the shop and was told that it was not the pump but the fuel pressure regulator. Its getting replaced as I write this.

mrdood · #5 03-30-2005, 12:24 PM

Hey this is familiar, My sub came back from "Getting fixed" but now takes up to 3 minutes to get it started when cold, I cycle the key about 8 times and then crank a few more before it will barely start, and then I have to hold the gas pedal until it is warm til finally it will hold its own idle. I think my problem is more involved but I would take any ideas and hopefully you will post your results reguarding FPR and FP.

wwixted · #6 03-30-2005, 03:25 PM

Dude:

I've had the exact same problem with my 97 Chevy Suburban. Four fuel pumps in 2 years, replaced the harness, wires, etc.

2 weeks ago, the mechanic found a fried relay - hooray! found the source of the problem - NOT.

Drove the Sub 900 miles straight to Atlanta without a problem - then - the crap starts all over again. Turns out the "box" the relay is in has now totally fried, melted the new relay, etc. THE SHORT IS WHAT'S CAUSING THE LACK OF FUEL PRESSURE. HIT A BUMP AND THE FUEL IS CUT OFF. GM's solution is $1200 for a pre-wired replacement. My mechanic is rewiring the whole thing for $300-400. Hope this finally cures the beast. I love the truck, but it may have to go if I burn thru this many fuel pumps!

Hope this helps!

mrdood · #7 03-30-2005, 03:34 PM

WWixted, thank for the info.
I have wondered about that sort of problem. Mech. earlier fix (to at least get it to run) was finding a shorting wire in the harness (I have yet to determine where). I was thinking along the lines of going to a higher volume FP and figure I would rewire mine with bigger wire anyway. I will see also if this helps my problem also.

sassee · #8 03-31-2005, 12:35 PM

Check the green wire on the fuel sending unit in your tank. It's the one powering the fuel pump. Mine was melted! turns out, a lot of others were too!

IHNZDUK · #9 11-22-2005, 07:19 PM

I've been having starting problems also...Ends up the corroded positive battery terminal was the culprit. Upon battery replacement, it was found that the bolt receiver(?) similar to a cylindrical nut in the battery, spun out. What ever...new battery and it works fine. I was going to do the pump relay, pressure sending unit etc, etc. So, check the bat before you spend alot.

mrdood · #10 11-23-2005, 12:00 PM

Thanks, for the response. And What I've done to correct my Rough problems...
1. cleaned out all of the carbon buildup in me TBI. I'ts pretty easy, might want to have a new gasket ready, I actually tor it apart and washed it in the sink and physically cleaned out the vacuum orifices.
(At the same time I added the TBI spacer and Fuel Injector Spacer)

2. the Water Temp Sender was bad (stuck) it always told the computer that the engine was hot, thus, not enough fuel let through to the injectors.

3. Replaced oxygen sensor.

4. found the stupid timing wire on the drivers side of the firewall (took a long time to find this bugger) and set the timing to +5 deg. ( I still have a pinging on hills so I may go back to +4 deg oor I may need to replace my knock sensor).

5. Also figured out how to adjust the Transmission kickdown cable so even the shift points are better for my truck.

Runs better than when I bought it now... I can get 12mpg instead of 10mpg.

Hope this can be of help to someone.....

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