Fuel pressure regulator leaking internally?

[Rollybear1]

Hello all, my 98 1500 stock 5.7L vortec (185k miles) started having long crank issues. Put a fuel pressure gage on it and when the key is turned on, the pressure jumps to 62-64. But as soon as the relay clicks the pressure drops to 0 within 15 seconds. Pulled the plenum top expecting to see the regulator leaking but see nothing coming from the vacuum port. Pulled each injector, pressurized the system and no leaks noted.
Can the regulator leak internally? Can it Bypass to the return without a visible leak? Im pretty sure the pump doesnt have a one-way for the return, or am i wrong? I just dont know where that 62 psi is going so quick.

thanks in advance!
Dave

 

[east302]

The pump is supposed to have a check valve, so it could be relieving back that way. Or through the regulator into the tank.

Best way to know for sure is to isolate the supply and return lines. There is supposed to be a union in the return line near the filter so that you can put a valve there. You would add another one in place of the filter.

With the return closed, you would prime the pump and if it holds then you know it was the regulator. If it dropped then it’s going out an injector or back into the pump. Open the return, prime, close the supply and kill the ignition. If it holds then it’s the pump. If it drops, it’s an injector.

50/50 shot, but a new regulator is a lot cheaper and easier than a pump. Plus it’s easier to return it.

 

[stutaeng]

I've never had to do this, but there are flex lines underneath the fuel lines that jump from the frame rail into the bell housing. They make special hose pliers. I would attempt to pinch the return hose down there and see if the pressure holds.

The fuel pressure regulator can cause low pressure because the spring inside allows too much pressure back to the return line. Very likely your issue, but gotta do all other checks before condemning parts.



There's a recent thread of a member having low pressure that turned out to be a blown hose on the fuel pump he'd just replaced recently. In that case, fuel was seemingly just being lost inside the tank.

 

[Rollybear1]

Thank you both! I'll post what I find.

 

[Rollybear1]

Installed new regulator and didn't change anything. $61 so no great loss. Oh well, it still runs pretty good, maybe better. I haven't test driven it yet. Fuel pump is what's left in the system and I've got one in the garage that I planned on installing eventually so I'll post after that.

 

[C30454]

Hello all, my 98 1500 stock 5.7L vortec (185k miles) started having long crank issues. Put a fuel pressure gage on it and when the key is turned on, the pressure jumps to 62-64. But as soon as the relay clicks the pressure drops to 0 within 15 seconds. Pulled the plenum top expecting to see the regulator leaking but see nothing coming from the vacuum port. Pulled each injector, pressurized the system and no leaks noted.
Can the regulator leak internally? Can it Bypass to the return without a visible leak? Im pretty sure the pump doesnt have a one-way for the return, or am i wrong? I just dont know where that 62 psi is going so quick.

thanks in advance!
Dave

You can have long crank issues for several reasons besides fuel pump issues. While I have heard people lament that fuel pressure should hold for some period of time when the pump stops running, as a 40+ year ASE Master L1 tech specializing in Domestic vehicles I have NEVER found pressure fall off to be any sort of reliable indicator of fuel supply system function. How LONG is it cranking? Do you have the equipment to read sensor data?

Rush to judgements are RARELY = succesful repairs. YESTERDAY, my brother called me about the '99 K2500 he is fixing up to sell. Out of the blue it wouldn't start after just driving it. Just cranked over. Everyone around him assumed it wasn't getting fuel. I got on the phone and after a few questions told him to hold the pedal to the floor, and it started. It was flooded. Then everyone around him told him his pressure regulator or spider assembly was leaking.

He brought it to me, and the coolant sensor was reading 5* on a warm engine because the sensor terminals and those in the pigtail were corroded. The incorrect temp reading caused the flooding and long cranking. There was NO coolant sensor code and no check engine light, because 5* is a plausible reading. A new sensor and pigtail fixed his flooding/fuel supply issues.

So bottom line, don't jump to conclusions, or follow other people's jump to conclusions.

If the engine is being over fueled for any reason, it should start quicker with a fullly depressed throttle. With the repeat of this simple test you should be able to conclude whether the motor is flooding from a leak or not without taking anything apart.

Is it always slow to crank, or just sometimes? And under what conditions?


Tom

 

[HotWheelsBurban]

I had long crank issues on my 99 Burb,5.7 Vortec, and assumed that it was just the fuel injection components being a little tired after 200+K city driving. Still likes a few seconds "priming" holding the key in Run before moving to Start, but other than that, issue was solved with new starter and battery. It had been something we got used to, "well it's just how it is", but after hearing the new starter sound 500% better, I know it being very tired was a lot of the problem. I wasn't as surprised about the battery, because it was over 3 years old, and that's about all I get out of one in Houston.

 

[Pinger]

Do these trucks have a fuel pressure accumulator? Without one surely the slightest leak-off will drop pressure dramatically?

 

[Rollybear1]

You can have long crank issues for several reasons besides fuel pump issues. While I have heard people lament that fuel pressure should hold for some period of time when the pump stops running, as a 40+ year ASE Master L1 tech specializing in Domestic vehicles I have NEVER found pressure fall off to be any sort of reliable indicator of fuel supply system function. How LONG is it cranking? Do you have the equipment to read sensor data?

Rush to judgements are RARELY = succesful repairs. YESTERDAY, my brother called me about the '99 K2500 he is fixing up to sell. Out of the blue it wouldn't start after just driving it. Just cranked over. Everyone around him assumed it wasn't getting fuel. I got on the phone and after a few questions told him to hold the pedal to the floor, and it started. It was flooded. Then everyone around him told him his pressure regulator or spider assembly was leaking.

He brought it to me, and the coolant sensor was reading 5* on a warm engine because the sensor terminals and those in the pigtail were corroded. The incorrect temp reading caused the flooding and long cranking. There was NO coolant sensor code and no check engine light, because 5* is a plausible reading. A new sensor and pigtail fixed his flooding/fuel supply issues.

So bottom line, don't jump to conclusions, or follow other people's jump to conclusions.

If the engine is being over fueled for any reason, it should start quicker with a fullly depressed throttle. With the repeat of this simple test you should be able to conclude whether the motor is flooding from a leak or not without taking anything apart.

Is it always slow to crank, or just sometimes? And under what conditions?


Tom

Thanks Tom. Your right, dont jump to conclusions. A little history on mine, I bought it Feb 22. Noticed the fuel pump was extremely loud. I could here it while driving. Then one day it got quiet, like it was a normal pump sound and thats when the long crank started. Long crank is about 5-6 seconds of cranking and then starts. Did the fuel pressure check and found it low...ish (55) and noticed it bled off immediately when the relay clicked off.
Thanks for your input. Much appreciated.