Fuel Problem???

[Guntherx]

So it happened again. I'm running along fine, and start getting into the throttle more, floor boarding it to see if it will make smoke (fuel turned all the way up, thanks Moose). All of a sudden It starts to die. I get on the side a keep running slow limping home. I stop for about 10 mins letting it idle. I come back and its running ok again.

This happened a month or so ago and I changed filter and it ran good again. Here is what I have. Aftermarket 40 gal rear tank. Carter P4070 electric fuel pump on teh rail 72 gph, 6 psi max about 2 years old. The problem I'm having is recent. It had been doing fine. I'm not sure if it is fuel pump going, debris in tank that gets sucked up, or an IP problem beginning. I will say I haven't been able to make it smoke much running empty, and not able to get the pyro up to 1300 easily.

I can't try front stock tank because it has a hole in it that I haven't had a chance to fix yet. So where would you start?

 

[IDIBRONCO]

I'd try changing the filter again. If a new filter fixes the problem, you might have some gunk in the tank.

 

[icanfixall]

Well my oppinnion is your running out of fuel at full throttle. Now trying to figure out why is next. What would be really helpful is to actually see the fuel pressure after the filter has done its job filtering the fuel. On the injection pump side of the filter there is a vacuum switch that shows what pressure or vacuum the line from the filter to the injection pump has. Normally if you have a restriction like a dirty filter or a bad lift pump it wil turn on the dash lite telling you the filter is dirty. That bulb could be burned out. Usually those lites are turn on when you first switch on the ignition switch. Thats just the way the designers fixed this to show whats working and whats not. If its been a long time since you scanned these gauges it might be a good time to watch them. I know the water in fuel lite comes on as does the abs lite and I think its the filter lite. Its been a long time for me too. Also there is a vacuum lite. I know mine has not worked in many years. Never figured it out why it doesn't work. The sender is the tuna looking can found usually on the passenger fender well.

 

[OLDBULL8]

Patch the hole in the front tank. So you can use it. Had a similar problem on my 84 Class3 MH. Rear tank rubber hoses to the FSV sloughed off bits of rubber and plugged up the carb, could have been the shower head disintergrating also. Actually put a new rear tank on and all new hoses. Ran just fine on the front tank after I cleaned the carb out. Thank God it didn't happen going thru Downtown Detroit, still had 50 miles to go to the campground, limping along at 25 MPH.

 

[Guntherx]

Well my oppinnion is your running out of fuel at full throttle. Now trying to figure out why is next. What would be really helpful is to actually see the fuel pressure after the filter has done its job filtering the fuel. On the injection pump side of the filter there is a vacuum switch that shows what pressure or vacuum the line from the filter to the injection pump has. Normally if you have a restriction like a dirty filter or a bad lift pump it wil turn on the dash lite telling you the filter is dirty. That bulb could be burned out. Usually those lites are turn on when you first switch on the ignition switch. Thats just the way the designers fixed this to show whats working and whats not. If its been a long time since you scanned these gauges it might be a good time to watch them. I know the water in fuel lite comes on as does the abs lite and I think its the filter lite. Its been a long time for me too. Also there is a vacuum lite. I know mine has not worked in many years. Never figured it out why it doesn't work. The sender is the tuna looking can found usually on the passenger fender well.

God idea about checking the light at startup. I know it did work because I would see it come on during long hard pulls after I put the 40 gal rear tank on, but it would keep running. I turned the mount in the top of the tank to get better alignment on the hoses and I never saw it come on again. When this happens it is sudden as if someone pulled the plug. It will start to miss and have no power at all. What surprised me is after idling for 10 mins or so it ran fine again. This only happened when I was trying to make smoke and get on it hard. I have to hook up the trailer and get a horse and am a bit worried if I'm in full throttle again.

Is there anything in an IP that might cause something like this? At the moment I'm leaning towards gunk in the tank. I might drop 5 gals in front tank and give it a try. The hole is over 1/2 tank. Anyone else have any issues with fuel lines coming apart? I know it was a problem on CAT engines where the line would swell closed.

 

[icanfixall]

If you running off only the one tank try bypassing the tank switch over valve. Just run a jumper line of 3/8 hose for the supply line and 5/16 for the return line. If you can run at full throttle after the bypass then you know there is crap plugging up the valve. They appear to be unrepairable but we have taken them apart by grinding off the case rivets. If you remove the switch you wil see what I'm talking bout. I think oldbull figured out how to repair these expensive switch over valves.

 

[79jasper]

I had the same problem with my PSD.
The shower heads had broken off and a piece was sucked into the line.

At first it was like you described, then got to a point it would do it every ¼ mile.
The tsv has some sharp bends and small passages.
I took the lines off mine and blew through all the holes, then flipped the switch and did it again.
Plus the lines going forwards, and the inlet and return lines to both tanks.

IIRC, I used maybe 30-45psi as that's the lowest setting I had.

 

[Ugly Moosling]

What about a partially plugged tank vent or cap? Could be pulling a vacuum on the tank when you're using a lot of fuel. If it's only partially plugged, once it idles for a while it could balance the pressures out.

 

[79jasper]

That's also a good point. Right before my first mechanical pump failed, it was pulling a good vacuum on the rear tank. Hasn't done it since.
Or maybe that caused the pump to fail, either way, good idea to check it.

 

[Guntherx]

I spoke to a diesel mechanic and he mentioned it could be getting air. I have replaced return lines and o-rings. When that happened the problems were starting after it sat overnight. I do have a little weeping of fuel around the sensor plug on top of the filter housing. I read where there is an o-ring in there that needs to replaced. I don't think it could possibly get air there when fuel is getting pushed in from the pump. Any thoughts?

 

[Guntherx]

I put furl in the front tank tonight and got on it. Woo wee Black smoke and power galore. Hehe. I was coming up a hill just half throttle and switched back to rear tank. Wow power dropped off noticeably. At least now I have a good idea where to start.

 

[icanfixall]

Well thats the game now. Theres hope now all you need to do is figure out why the rear tank has a suction issue. Thinking about blowing out the lines back into the tank wil only cause you to suck it up again. Sadly the tank has to come out. Then blow out the lines and then clear the sender suction line too.