W24 hard to start (fuel delivery?)

[toasty]

Hey, WH people!

We've got an '06 Gulfstream Sun Voyager on a W24 chassis. Just recently it's become rather hard to start after the engine has been off for more then a few minutes. It cranks fine, just sounds like it's not getting any gas. Running the starter for about 10 seconds and it'll get a few spurts of fuel, then start and run great. No loss of power or anything. If I shut it off and immediately restart it'll come back just fine.

No gas leaks I can see anywhere, no smell of gas after it does start, so I'm guessing the fuel pressure is low or it's running back into the tank after shutting it off.

I replaced the fuel filter on the chance it was clogged(the awesome kit from oem-engineering.com), but no difference. Short of dropping the tank to change the pump, is there anything easier I can check first? Is there a check valve near the engine somewhere, or could this be something different entirely?

[oemtech]

If you turn the key on you should hear the pump start. Check the fuel rail pressure at the Schrader valve. It should be 55 to 62 PSI.

[toasty]

There's just one pump, and it's inside the tank, right? I don't hear anything from the driver's seat, so I just want to make sure.

And the valve is near the engine, only accessible from the top, through the dog house?

Sorry for all the questions, just want to double check before I unglue my carpet!

[oemtech]

Yes, pump is in the tank. Let the rig set for 24 hours. Now go to area where the tank is located and have someone turn on the key. You should hear the pump star and pressurize the fuel rail. The pump puts out about 90 psi and the fuel rail regulator drops that to 50 to 62 psi.

The Schrader valve can be accessed from under the rig if necessary. I know Gulf Stream makes access to the engine from the dog house a real PITA. Here is a photo of the fuel rail test on my coach. You can see the hose connection to the valve just below the dip stick tube... its the shiny thing.

[toasty]

Thanks so much, that made finding it much easier.

This is what I found:

Before touching anything, I connected the gauge and found 0 PSI.

Turning the key to RUN, the pump comes on for a few seconds then stops. The pressure goes up to around 60PSI pretty quickly. When the pump stops, the pressure drops back down to 0 very rapidly.

If I run a jumper over the fuel pump relay to keep the pump running constantly, it stays around 60 constantly. Fuel pump draws about 5A while running.

So, it sounds like the pump is working, but it's just not keeping any pressure after it turns off. I'm guessing that's not normal. Does anyone know if there's a check valve somewhere that might be stuck open?

[edgray]

Hopefully you'll find the cause of the rapid loss of pressure upon shutdown, however that may be deemed "normal" by those here who know.

Regardless, the engine "should" start right up EVERY time you want it to ASSUMING you leave the key in the "on" position for a few seconds before moving the key to the start position. As for me, I always turn the key to "on" and then I wait until the IP stops beeping before starting the motor. Ed

[Mutha]

Quote:

Originally Posted by toasty ............Does anyone know if there's a check valve somewhere that might be stuck open?

You are correct in that the pressure should remain over 45 PSI for at least 4 hours when the engine is shut down.

My guess is you have a stuck open "fuel pressure regulator valve" located in the top part of the in-tank fuel pump. You might try blowing compressed air through the upper return fuel line located on the front of the fuel filter, being sure the gas tank filler cap is removed when blowing the air through the line. If this doesn't work, you will probably have to remove and replace the fuel pump. Good luck!

[toasty]

I tried the air compressor trick and didn't solve it.

A mechanic friend suggested trying a couple of cans of Seafoam thrown in the gas tank to try to ungum it, which so far hasn't worked either.

Still fiddling before I give up and drop the tank.

[toasty]

Quick update:

Seafoam didn't work either. Looking at the tank, I don't think it's something I can remove at a campground without more tools than I brought with me.

I've tried the nearest 4 Workhorse service centers and another couple of big truck repair shops near me, and not having much luck with anyone wanting to do this and/or thinking they could get it done same day.

Still working on it!

[toasty]

Hey, Oemtech... Your page ( Oemy's Web Site - Workhorse Parts Xref W Series ) lists compatible fuel pumps, but the cross reference guide I have says that's only good up to the 2003 model year. Do you know if those will work on later model years?

[RocketDork]

You could also check for a leaking injector(s). If the system is losing pressure quickly, you've definitely got something wrong.

Based on the symptoms you've described, I'd be willing to put a friends bottle of beer as a bet on an injector leak.

[toasty]

If that were the case, wouldn't I be seeing some other symptom other than just cranking with no fuel for 10-20 seconds?

Once it starts running it's perfectly smooth, no loss of power since this started, no fuel smell near the engine or exhaust, no rough idle or anything. If I force the pump to stay running when the engine is off, I'm not getting any leaks I can see/smell either.

Not saying you're wrong, I'm just grasping at straws here.

[RocketDork]

It could be possible, and I say "could" because I'm the dumb one in the room, that the injector is leaking "slowly" compared to engine RPM, and thus only effects things slightly when the engine is running...but when the engine stops, the leak becomes "big" by comparison to holding pressure for hours...

I don't know if the above makes sense.

The reason I say injector is because, when shut down for a few minutes its hard to start. If it was just the pump letting fuel flow backwards to let pressure decrease, it would start the same as when its sat for weeks/months...meaning quickly without a sputter.

You say, if you let it sit for a while, it will start with a "few spurts of gas", which I took to mean that it tries a few times before running normally. My theory is that the engine is "flooded". The injector has leaked down and put a bit of fuel into the intake. If you crank for a bit, then it kind of clears things out and the engine runs.

If you let it sit for long enough for the gas to evaporate, I'm betting it would start as "normal" for a cold start.

I don't know...I'm kind of grasping too.

[toasty]

Okay, sorry, bad description on my part.

If it's running, and I shut off, and restart within maybe 10 seconds it's fine.

If I wait 5 minutes, it's 10-20 seconds of cranking with absolutely no sounds of life at all, a few seconds of it nearly starting (RPM gauge jumps a few times), then it finally catches and runs fine. I'm holding the starter down the whole time, and once it starts at all, it's completely stable and happy.

I know it's a fine line, but it's not sounding flooded, but more like trying to restart an engine after running out of gas completely. If I wait 48 hours, it's exactly the same thing, which was how I was ruling out it leaking out the other way. Just as hard to start, and takes just as long.

You've inspired me to recheck the injectors though, I'm not so certain that I won't double check before ordering a new fuel pump assembly!