Fuel Pump Issue???

[boatman10]

If someone turns the key on after it has sat for awhile with you laying underneath the unit at the tank and you do not hear the pump buzz for 2 seconds to pressurize the fuel rail, and While it does not work as good it seems on GM stuff compared to other makes, a clunk on the bottom of the fuel tank with a rubber hammer [or anything handy at the time, really] with the key ON can jar a dying fuel pump back to life to get you home/to a mechainic.


That worked for me in my chevy 4.8 pickup truck, but only a coupla times........and the girl across the street did this for a YEAR intermitantly with a Lincoln.


I can hear the fuel system pressuring up in my P30 at the drivers seat on key-on, after sitting off for only minutes.

[AKIQPilot]

Originally Posted by boatman10

If someone turns the key on after it has sat for awhile with you laying underneath the unit at the tank and you do not hear the pump buzz for 2 seconds to pressurize the fuel rail, and While it does not work as good it seems on GM stuff compared to other makes, a clunk on the bottom of the fuel tank with a rubber hammer [or anything handy at the time, really] with the key ON can jar a dying fuel pump back to life to get you home/to a mechainic.


That worked for me in my chevy 4.8 pickup truck, but only a coupla times........and the girl across the street did this for a YEAR intermitantly with a Lincoln.


I can hear the fuel system pressuring up in my P30 at the drivers seat on key-on, after sitting off for only minutes.

Yes, that can work for sure. Especially on a motorhome with a steel tank.

[Vroom]

Can anybody elaborate on the external fuel line check valve that M&EM writes about in their post in this thread. This could work for me as I have a 2004 P32 8.1 ltr that will not hold fuel pressure for more than 30 minutes or so after shut off. With less then 15K miles on my rig I have perfect fuel pressure but I've been told that the internal check valve in the fuel pump possibly has some corrosion from age and can't hold pressure. Something like this may be a long term fix until the pump actually needs to be replaced. Thanks for any and all replies.

[M&EM]

VROOM, The check valve kit I used looks like this. Go on line and search for "fuel line check valve". They are around $35. Mine was for a 3/8" fuel line. I installed it between the tank and the filter (2003). I believe 2004 and later chassis rely on a different pressure regulator located in the fuel pump canister so the check valve may work better engine side of the the filter. Comes in 5/16" or 3/8". Measure your fuel line!! I used a compact tubing cutter to cut the fuel line in the chassis rail.. After I installed it my pump ran for another 5 yaers and finally failed at 95000mi. HTH..

[Vroom]

Thank You M&EM,
Yes , this is going to help "Big Time". I had the MH pulled on the driveway and ready to disassemble to drop the tank. This is the next best thing to a day off. One more question, is it the O.D. measurement of the tubing I want? Thanks again and I'll stay in touch with an update.

[Vroom]

M&EM,
I found the exact one that you pictured!

[M&EM]

Vroom, measure OD for the pictured check valve. It is a compression type connection in and out. Before you cut confirm that check valve actually works!!

[Vroom]

M&EM,
Ordered my fuel line check valve. Do you think that the closer I install it to the fuel pump might be better as it would keep more of the fuel line under pressure. That way there would be less possible "down stream" bleed off at the original leaking check valve at the pump. Thanks for your time.

[millsrv]

The fuel pump check valved failed on our W24 a few months ago when we were 3000 miles from home. I am a retired mechanic and actually had a fuel pressure test gauge with me. I saw the pressure bleed down to zero within a few seconds after shutting off the engine. When the engine was running the pressure was completely normal. The symptom as you would expect was an extended cranking time. I simply turned the Ignition on and off several times before cranking. This worked to prevent the long crank before starting.
The stuck open check valve unstuck itself the next day and has not been a problem since.
It is unfortunate that the valve is part of the pump module. I am not excited about the idea of cutting the steel fuel line to install a check valve but I most likely will do just that before spending north of $500 for a pump and working for hours to replace it simply because of a plastic ball not seating properly.
As a mechanic I have replaced many GM in tank fuel pumps. Most of them will not run and pump after being shut down. I was able in many cases to get the failing pump to run by bypassing the relay (energizing the pump) and banging on the tank with a rubber mallet. At least then I could drive the vehicle into the shop.

[M&EM]

Vroom,
Yes. I located the check valve on the tank side of the filter on my repair. As long as your pump still provides correct pressure when engine runs, you could do the same. It's not real clear in the photo of above post # 18 where the check valve is shown. But I had a straight section of fuel line long enough for the valve. I used a very compact tubing cutter for the first tank side cut. I was able to remove the tube to the filter and cut a piece out equal to the length of the valve. Any cuttings got caught in the filter.

HTH

[Vroom]

M&EM,
I was in position to do the first cut on my fuel line just before the filter, absolutely perfect location, when I noticed that the fuel line just to the other side of the filter has an inline "T". It appears that one line goes to the engine and the other line returns to the tank. I don't see how the check valve is going to hold pressure when there is an open return line going back to the tank. I haven't had any luck finding a fuel line schematic explaining this type of system only that these were put in place in 2004. The only info I've gathered is that it's called a "return line less" system to alleviate vapor lock. At this point I'm not sure where to put the check valve and I'm not much for guessing but I'm thinking about installing it just to the engine side of the "T". Maybe somebody out there is familiar with this layout and can help with the correct location for the check valve. Thank You.

[millsrv]

Originally Posted by Vroom

M&EM,
I was in position to do the first cut on my fuel line just before the filter, absolutely perfect location, when I noticed that the fuel line just to the other side of the filter has an inline "T". It appears that one line goes to the engine and the other line returns to the tank. I don't see how the check valve is going to hold pressure when there is an open return line going back to the tank. I haven't had any luck finding a fuel line schematic explaining this type of system only that these were put in place in 2004. The only info I've gathered is that it's called a "return line less" system to alleviate vapor lock. At this point I'm not sure where to put the check valve and I'm not much for guessing but I'm thinking about installing it just to the engine side of the "T". Maybe somebody out there is familiar with this layout and can help with the correct location for the check valve. Thank You.

The pressure regulator is at the end of the "return line". The supply from the pump is where the check valve is. If the return line was simply open there would be no fuel pressure right?

[Vroom]

MILLSRV- Jim,
Pre your reply- Right, I'm thinking that I should be able to install the check valve exactly where I original wanted to, just before the filter. Boy, am I glad to hear from you, I've been grinding over this situation all day. Jim, thanks for your time.

[M&EM]

Vroom MILLSRV is absolutely correct. However it will work just fine any where on the fuel line.
Be sure you test the check valve BEFORE you install it!

Marty