237 Fuel Delivery System

[jakebrake86]

I've got a new problem I was wondering if anyone could help me with. First of all, I'm no engine man...I do good to call myself a truck driver LOL. Anyway, the other day my dad found a good deal on a 1974 RS600LS and decided he'd lay down the $2500 and try to use it as a site truck. He used it for a week or two before it came time to drive it 200 miles in 12 degree weather to the Vicksburg yard. I was driving and had gone about 4 miles when it seemed to run out of fuel and just die. The tanks were full so we changed the filters. That worked for another 4 or 5 miles until it did the same thing again. We kept stair stepping our way until we limped a grand total or 25 miles and stopped in Clarksdale in a legion hut parking lot. We got a real mechanic to look at it and he said it was sucking air at the primer pump so we plugged it like it is on all of our other trucks... This time it wouldn't even crank. Finally we changed the supply pump but that didn't seem to make any difference. The truck is still sitting in the legion hut parking lot to my knowledge (havent talked to dad in a week) but does anyone have any ideas? My uneducated guess is that the injection pump is bad...

[Mack Doctor Jr.]

There may be a chance there is a colapsed fuel line. Ive had this happen to me years ago it kind of did the same thing. Try taking them off at both ends one at a time not to mix them up up and blow air through them (air comp.) put your had over them to check flow.

I used to keep a little propane torch with me in the winter to heat up the 90 degree fittings when i would gell up wich may also be the case too. Thats one thing to remember try to use less 90's when plumbing fuel it can cause problems in the cold.

[HK Trucking]

You say the temp. was 12 deg., possibly the fuel was gelling up? Have you tried it since the weather warmed up? Did you put any anti gel in the fuel tank(s)? A combination of fuel thats on the verge of gelling plus old deteriorated fuel lines on the suction side (ie from tank to pump) could cause it to suck air when under normal conditions there would be no problem. If you took out the primer pump & put a plug in its place be sure the spring & stuff is stillthere before putting the plug in or the supply pump wont work. I'd say put the primer back in & try to pump up fuel manually til there is pressure felt against the plunger when pumping it then loosen off the injector lines & crank the engine til fuel squirts out, tighten the lines & see if it will start. Hope you get er going! Herb

[Lmackattack]

it does sound like an air sucking issue. If it starts and runs then quits that means that it can supply the engine with fuel untill to much air enters and the prime is lost. if all the lines are good and not craking etc.. look in the fuel tanks for dirt or rust etc... I have heard that the pick up tubes at the top of old fuel tanks rust and may allow air to enter the lines. wile there, check to see if the pick up tupe is clogged. If you removed the hand primer its likely the fuel drained all the way back to the tanks. you may need to force air into the tank and help the fuel get into the lines again to start it? after it starts crack the injectors one at a time and wait for the chugging to stop then tighten them.

[jakebrake86]

At one point or another, we did everything that I can think of... We were contiuously blowing fuel through lines with an air compressor... We would make sure the filters were full, disconnect the supply line at the primary filter base and blow air into the tank to push fuel out the line. When we got fuel, we would hook the line back up, loosen the injector lines at the pump, and wheel it over till she was spurtin'. We would tighten it up and try to fire it up, and up until the last time, it would do fine for about 4 or 5 miles... We put fuel conditioner in the tanks and even had a butane torch to try and heat up fittings the first day when it was cold. The next day, though, it warmed up to the high 40's (strange weather in the Delta) and we were having the same problems... One thing u mentioned, Herb, I'm not so sure about. I cant remember if we put the spring back in when we plugged the primer or not... I'll check on that. Thanks for the help, guys!!

it does sound like an air sucking issue. If it starts and runs then quits that means that it can supply the engine with fuel untill to much air enters and the prime is lost. if all the lines are good and not craking etc.. look in the fuel tanks for dirt or rust etc... I have heard that the pick up tubes at the top of old fuel tanks rust and may allow air to enter the lines. wile there, check to see if the pick up tupe is clogged. If you removed the hand primer its likely the fuel drained all the way back to the tanks. you may need to force air into the tank and help the fuel get into the lines again to start it? after it starts crack the injectors one at a time and wait for the chugging to stop then tighten them.

Well, we did all that... We even pulled the intake tube out and it was fine... I think it was copper but it wasnt rusted or corroded or anything. We blew it out, then pushed fuel back to the motor and it would still do the same stuff, so I'm guessing by what yall are telling me is that the old fuel lines are probably just bad and pulling air through them somewhere... I know the truck sat for at least a year or so without being used so that must be it. And I bet the reason it wont crank back is we must have forgotten to put the little spring back in the primer port on the pump. For the life of me I cant remember if we did or not. I'll check on it first thing 2morrow. Thanks Again Everybody!!!

[bowtiebulldog]

You might want to try this simple check.

Are your tank vents clean? It sounds like it could be a simple vent cleaning to fix your problem.

If your tank vents are clogged, you will NOT draw fuel from the suck tank( right side ). You will draw just enough to run for a few minutes because everytime you open the system you give it air.

[MidniteMechanic]

Also check in the tanks for junk. Things like the foil from fuel treatment bottles have a funny way of getting in there. Or the chains off the fuel cap will cause problems. It depends how the system is plumbed, one tank will suck dry and the other tank will still be full or overflow due to fuel being returned but not used. It will drive you crazy til you find it.

[dendrill]

When i first got my gmc with the detroit it would fall flat on its face pulling a hill (more than usual) i pulled the pickup tube and found a small piece of foil, looked like a diesel fuel only sticker, i guess it would suck up there when i really poured it on but would allow enough fuel under other conditions.

[David]

Had this problem once. Turned out to be a hole in a metal fuel line on the suction side. Look where ever the line may be rubbing against something.