Fuel pressure problem

[sy2756]

I tested my fuel pressure according to the GM shop manual. Key on fuel pressure rises to 45 PSI and then immeadiatly drops to zero when the pump shuts off. I start the pump with a jumper and pinch the supply line off then stop the pump pressure drops to zero. Repeat the test with pinching the return line off drops to zero. The book says I have leaking injectors, so I pull my plugs for inspection, they are dry and have no gas odor.

My truck is stock. Any ideas?

 

[atc82]

if the presssure bleeds off quickly when pump is shut off like you are stating, i would suspect the fuel pressure regulator. is this a stock regulator or and adjustable one? it should take a very long time for the pressure to bleed down.

 

[sy2756]

It is the stock regulator.

 

[SY756]

Sounds like you have a big leak somewhere. Take off the vaccuum line going to the FPR and start the pump up. If gas shoots out the port then you have a blown diaphram in the regulator. If not then I would suspect a leaking injector. BTW, how's the truck running? Rich, stalling, etc, etc.

 

[sy2756]

No fuel pouring out of the regulator. Truck idles rough, stalls sometimes, and sometimes misses at idle.

I removed the upper intake and ran the fuel pump to look for a leaking injector, they do not appear to be leaking.

Whatt are the chances that I have two problems, bad regualtor and bad fuel pump?

 

[BobbyFresh]

Probably the one way valve in the pump or possibly the fuel pressure regulator . My geuss would be the pump

 

[jwaller]

your problem is more than likly inside the tank. either your pump has a bad check valve or your pulsator is leaking. remove the tank and install a real pump and delete the pulsator. a 255 hp would be best.

 

[sy2756]

I have confirmed that I have two problems. Both the FPR is bad and I have a problem with the fuel pump.

I replaced the FPR and restested by building pressure and then blocking the supply line, the pressure held this time.

So all I need to do now is replace the fuel pump. Is it better to drop the tank or remove the bed?

 

[myclone]

If you can round up 3 or 4 buds to help lift it then its easier IMO to remove the bed. Its not that the bed is that heavy its just too bulky for two ppl (unless of course those two ppl are power lifters).

 

[just a 6]

You don't need any help at all if you do it this way:

http://webpages.charter.net/syclone2550/fuel.htm

I tilted up my bed all by my self and it's not heavy at all if you do it this way.

If you can round up 3 or 4 buds to help lift it then its easier IMO to remove the bed. Its not that the bed is that heavy its just too bulky for two ppl (unless of course those two ppl are power lifters).

 

[Sy#26]

Or, if you're working alone, cut a hole in the bed. Replace w/ a hinge & stops pop riveted. Tank access seems never to be a one time thing....

 

[SY2932]

If you can round up 3 or 4 buds to help lift it then its easier IMO to remove the bed.

Yup, bed only weighs 230 pounds with tailgate... Depending on how "crazy" you are about cleaning/corrosion control, I think you would be better off pulling the bed. I pull mine to wax behind the cab and front of the box. Also to address corrosion on the frame by power washing it, wire wheel/scraper treatment, primer and then paint. I pull my bed by myself using my little finger :wink: http://huryde.station180.com/gallery/view_photo.php?set_albumName=mikecampbellakaSY2932&id=abq

BTW, if you opt to remove the bed, DO NOT lay it down on the cladding because you WILL break it. HTH's

Mike Campbell

 

[sy2756]

I like the idea of tilting the bed up. How many bolts hold the bed to the frame? What about the fuel filler?

 

[just a 6]

First you remove the valance/rollpan and disconnect any ground wires. Then loosen the filler neck from the bed and tuck it aside. Then remove bed bolts on driver side, i think it's 3 of them. On the pass side just loosen the bed bolts about 1/2", make sure they are still threaded to the bed. If you remove the pass bolts the bed will slide of the frame when you tilt it up. But with the bolts still in the bed but loosen enough you have enough play to tilt the bed and at the same time they work as a stop for the bed. Then you can lift/ tilt the bed with just one arm and put a jackstand or a piece of wood to support the bed in tilted position. The bed is really light doing it this way due to that you have some kind of lever effect because the overhang from frame to outside of the bed. Kind of hard for me to explaine in english, hope you get my point?

I like the idea of tilting the bed up. How many bolts hold the bed to the frame? What about the fuel filler?

 

[sy2756]

Cool, I will try it on my next day off. Thanks!

 

[InvisiBill]

http://www.sytyarchives.com/howto/viewarticle.php?article_name=bed_removal.php&dir=exterior

 

[sy2756]

Ok, I started this project and now have some new questions.

1. I have removed the old pump, I do not see the pulsator. So can I assume someone has been in the tank before me, or did some trucks not come with them?

2. My original problem was fuel pressure drops to zero when the pump shuts off. Isn't there supposed to be a check valve in the tank some where? And does the Walboro setup have a check valve?

Oh, BTW thanks for all the advice you guys have given me so far!!

 

[Sy769]

Ok, I started this project and now have some new questions.

1. I have removed the old pump, I do not see the pulsator. So can I assume someone has been in the tank before me, or did some trucks not come with them?

2. My original problem was fuel pressure drops to zero when the pump shuts off. Isn't there supposed to be a check valve in the tank some where? And does the Walboro setup have a check valve?

Oh, BTW thanks for all the advice you guys have given me so far!!

1.Pulsator is a black plastic box with a metal cover. If it is not installed there will be a piece of rubber hose between the pump and the metal tube. Gm installed them on all trucks as AFAIK.

2. Check valve is in the pump. Go ahead and put in a new Walbro high pressure pump and replace the rubber hose.