Had to call the tow truck today...

[Tyroma]

Hey Gang....

SO I have been working steadily on the M37 for a while, and have been out for a few jaunts with it. Today, I decided to run it into town. As I got to the highway (about 6km from home) she started to sputter and stall out...as if out of gas. She quit, and I coasted safely to the soft shoulder.

I was unable to get it started again. I must say, that those 24v systems will crank for a LONG time. After about ten minutes of fiddlin around with it, I called a friend who happens to own/operate a tow business, and on the deck she went.

When I got home, I got in the truck on the deck, and had planned to hold it on the deck until it was unhooked, and then used the slope to roll it to my shop. So I stepped on the brake, and poof...pedal went to the floor...blew a line in the rear. Good thing I was at home!

So I figured I'd start with the fuel pump...unhooked the line running to the carb, and turned over the engine...drip drip drip...hardly any fuel getting to the carb. Good thing I started there! So now I am thinking that it's the fuel pump..and I'm looking at it, and thinking "how the hell do you get at the thing to remove it?!?" Then I notice the little shut-off valve on the line right at the pump. The valve handle is pointed in the right direction, but I give it a few spins anyways.

I get the truck running with a pop-bottle full of gas and a rubber hose to the carb (gravity feed) and WOAH...the friggin fuel line from the pump is gushing fuel now!!! I re-attach the carb to the fuel pump line, and she runs again. I ran it at fast idle for about 15 minutes, and it didn't miss a beat.

What gives? Is it possible that the valve got full of crud, and got freed up by my spinning the valve handle? or should I be looking for something else? Any of you guys ever experince something similar?

Thanks!

Ty

[MSeriesRebuild]

If you haven't cleaned the tank and lines, it is a great possibility that rust and debris in the tank and lines is the deal. If that is the case, it will do it again as soon as some more of the junk lodges in something. The elbow coming off the tank top plate is usually the first killer area.

[Joe]

Charles,

What's the best way to clean those lines and fittings?

[MSeriesRebuild]

Charles,

What's the best way to clean those lines and fittings?

It can be done any number of ways depending on how bad it is, my opinion is this. If it's bad enough to be causing the type of issue that was mentioned in this thread, the best way is to remove the tank and send it out to a local shop for a serious cleaning and coating of the interior surface. Most radiator repair shops offer this service. Lines usually deteriorate from the inside outward, they are not expensive at any local auto parts outlet. My recommendation is to simply bend up a replacement and install all new line and hoses. It will be money well spent.

[Nickathome]

Pull your sending unit and check the fuel level. Your story sounds exactly like what happened to me about a year ago. I thought I had enough gas, but while out it ran out and left me stranded. I too thought the lines were clogged, etc, only to find out the float or something is causing my gauge to give me false readings. So now, when I see my gauge go below 3/8ths of a tank, I know I'd better find a gas station and quick.

Dollars to donuts you simply ran out of gas. When your lines surged at home its probably because you got some fuel into the lines, enough to make it appear as if a clog had dissipated. Pull unit and shine a light into the tank, My bet is you will see maybe 3/4th inch of fuel. If so, that's your problem, same as what I experienced.

[Tyroma]

Hey Nick...

I will pull the sending unit and check that..thanks! I am pretty sure that the tank was boiled and coated already, so I don't think it's full of rust.

Ty

[8543bob]

I TOO HAD A SIMNILAR PROBLEM WHEN I FIRST GOT MY TRUCK. IT WAS A RUBBER FUEL LINE, JUST BEFORE THE PUMP THAT HAD AN INTERNAL COLLAPSED, ALCOHOL IN THE MODERN FUEL CAUSES ALL SORTS OF PROBLEMS WITH THE OLD RUBBER.

[Tyroma]

Good News!

So last night, I pulled the lid off the top of the tank...I was pleased to find that the inside of the tank is bright, clean and shiny! There was, however, some grit and cedar leaves (??) floatin around in there...along with bits of the original cork gasket from the lid.

To my surprise, when I pulled the fuel pickup assembly out, I found there there was no filter on the bottom of the tube! Just an open 3/8" tube! no wonder something gummed up the line! Probably sucked a chunk of cork or cedar up there.

I checked the fuel guage sending unit while was had the tank open, and it does work..although I found that it will give an accurate reading while the ignition is on, but truck is off, but when the truck is running, it reads too high. Must be some electrical interference when the engine is running.

So I threaded the pickup tube, and installed a little aluminum in-line screen filter that I had kicking around, and then installed another in-line filter between the fuel pump and the carb. I made up a new cork gasket for the tank lid and put it all back together.

Today I bought a tow strap (...so the wife can come and tow me home if I should get stranded again ) and I am gonna try it out tonight.

Thanks all for the info/sugesstions!

Ty

[Tyroma]

I TOO HAD A SIMNILAR PROBLEM WHEN I FIRST GOT MY TRUCK. IT WAS A RUBBER FUEL LINE, JUST BEFORE THE PUMP THAT HAD AN INTERNAL COLLAPSED, ALCOHOL IN THE MODERN FUEL CAUSES ALL SORTS OF PROBLEMS WITH THE OLD RUBBER.

Maybe just to be sure, I'll replace that rubber hose with a steel fuel line or new rubber line...
Here's a pic of the setup that I found online

[Joe]

I checked the fuel guage sending unit while was had the tank open, and it does work..although I found that it will give an accurate reading while the ignition is on, but truck is off, but when the truck is running, it reads too high.
Ty

What you're describing used to be common. It's caused by the difference in the voltage when just the battery is turned on and when the engine is running and the generator is generating power. The battery is roughly 24 volts but the generator puts out roughly 28 volts (the battery will load it down to something less depending on it's state of charge). The generator output has to be higher so that the battery will charge. Your fuel level sensor arm is mechanically connected to a variable resistor and the gauge is basically a voltage gauge that displays the different voltage/current levels from the variable resistor. Your fuel gauge is varying because the vehicle voltage is varying. The way that they deal with that in modern cars is that they have a little voltage regulator under the dash that regulates voltage going to all the instruments so they get a constant voltage regardless of what the vehicle voltage is. IIRC it's about 5 volts. I don't know enough about the M37s to know how or even IF they regulate their instrument voltage but I suspect that they do and that it's done within the fuel gauge.

By any chance is your battery voltage gauge reading too high when the engine is running?? If so your voltage regulator is probably not working properly and the vehicle voltage IS too high and that's why your fuel gauge is inaccurate.

[Tyroma]

The saga continues....

I installed the little plastic see-through in-line filter and fired her up tonight...I now think that my pump needs to be rebuilt. Now that I can see what's going on inside the filter, I can see that at idle and at fast idle, the pump is barely putting enough fuel into the filter to keep the truck running. Further, I can see from the fluctuations in the fuel flow that it is not consistant..rather, the surges in fuel are random and sporatic.

What do you guys think? Should I get a kit and rebuild the pump? Where's the best source for pump kits? I found Then & Now Automotive.

Thanks

Ty

[MSeriesRebuild]

The saga continues....

I installed the little plastic see-through in-line filter and fired her up tonight...I now think that my pump needs to be rebuilt. Now that I can see what's going on inside the filter, I can see that at idle and at fast idle, the pump is barely putting enough fuel into the filter to keep the truck running. Further, I can see from the fluctuations in the fuel flow that it is not consistant..rather, the surges in fuel are random and sporatic.

What do you guys think? Should I get a kit and rebuild the pump? Where's the best source for pump kits? I found Then & Now Automotive.

Thanks

Ty

Then-Now.com has good fuel compatible kits, don't use a NOS kit whatever you do. If the diaphragm is breaking down, you should see black particles in you new filter. Be careful, if the diaphragm is cracked or torn, gas will dump straight into the oil pan causing oil dilution and disaster.

[Tyroma]

[quote="MSeriesRebuild]Then-Now.com has good fuel compatible kits, don't use a NOS kit whatever you do. If the diaphragm is breaking down, you should see black particles in you new filter. Be careful, if the diaphragm is cracked or torn, gas will dump straight into the oil pan causing oil dilution and disaster.[/quote]

Hey Charles...

So far, not black particles visible. I did find Then-Now.com and sent them off an email. I'll keep an eye on the filter. I guess this is just one more thing to fix...

Thanks

TY

[8543bob]

HI, BEFORE I FOUND THE PROBLEM WITH THE FUEL LINE, I THOUGHT THE PUMP WAS BAD, SO I INSTALLED A MILITARY BENDIX 24V FUEL PUMP, WITH AN INTERNAL FILTER. IT DID NOT REQUIRE A PRESSURE REGULATOR, I GOT IT FROM SAM WINER. AFTER I INSTALLED TH ELECT PUMP I HAD THE SAME PROBLEM. SHE WOULD DIE AT ROAD SPEED. THATS WHEN I LOOKED FURTHER AND FOUND THE BLOCKED FUEL LINE. I LEFT THE ELECT PUMP ON AND HAVE HAD NO TROUBLE SINCE.
GOOD LUCK.

[MSeriesRebuild]

[quote="MSeriesRebuild]Then-Now.com has good fuel compatible kits, don't use a NOS kit whatever you do. If the diaphragm is breaking down, you should see black particles in you new filter. Be careful, if the diaphragm is cracked or torn, gas will dump straight into the oil pan causing oil dilution and disaster.

Hey Charles...

So far, not black particles visible. I did find Then-Now.com and sent them off an email. I'll keep an eye on the filter. I guess this is just one more thing to fix...

Thanks

TY[/quote][/quote]

Particles indicate a gradual deterioration of the diaphragm or a rubber hose is in progress. A crack or tear can be present and possibly no particles will ever be seen. Hopefully you don't have this in progress, but is way to critical of an issue to pay no attention. A little gas in the crankcase will do some huge damage in a very short period of time. I would check it out just as a preventive maintenance measure.