6.9 quit

[Brian VT]

Was driving today, trying to sort out my C6's shift points, and got a couple miles from my house and the engine quit.
Prior to that when going uphill it ran a little rough and then on the flat it would "clean out" like when a 2-stroke hits the power band.
I've only put @ 20 miles on it since I got it. The other day I topped off both tanks because the gauge doesn't work and then I tried switching to the front tank and the engine quit after a mile or so. I switched back to the rear tank and got it running again and it seemed ok.
After it quit today and wouldn't restart I got a new fuel filter (even though the one on there looked new) and drove back to the truck (it's on the side of the road). I filled the new filter with Diesel 911 through the small holes and installed it. Tried starting again. No luck. Tried switching tanks. No luck.
Do you all have any ideas for me to try to get it started? If not I guess I'll need to have it towed to a mechanic.

 

[gandalf]

It sounds like a rather significant air intrusion. These are never good. Since it's affecting both tanks it must be between the FSV (the fuel selector valve down on the frame rail) and the engine. The FSV itself could be bad, or anywhere after it. I can't remember whether the '87 had the infamous water separater mounter on the driver side fender near the hood hinge, with a pull ring on top. Those have a very bad reputation. Or it could be any joint or connection along the way. It could even be the lift pump gone bad.

Try hooking up a jerrycan as close as possible to the fuel filter level. Have it feed directly into the fuel filter. The engine will run decently without the lift pump, but definitely lack high end grunt. Doing this you're bypassing virtually all the air leak areas.

Where are you in Maine?

 

[sjwelds]

Check to make sure you're getting voltage to the fuel shut off solenoid on your injection pump.

 

[Brian VT]

Thanks guys.
I had to have it towed but I'll throw those suggestions at my mechanic.

gandalf, I'm just north of Sebago Lake.

 

[Brian VT]

I replaced the vacuum modulator that morning. I reused the (old?) rubber hose that was there.
If I had caused a split in that hose would that cause the engine to quit?

 

[TNBrett]

No. Your issue will likely be fuel or electrical.

 

[lotzagoodstuff]

Take a look at your oil level. If the mechanical pump goes bad it could put some fuel in the oil, which would be an easy diagnosis. I’m the mean time, you could run a simple and temporary electric pump in place of your mechanical pump as they are a lot more tolerant to air intrusion.

 

[gmtech68]

My experience with a dead lift pump is it runs after the pump quits until it is turned off and will not restart. Good advice to start with a jerry can and eliminate that. Make sure the pump return line isn't blocked in the pump. Make certain the shut off has power like has been suggested.

 

[Brian VT]

So I had it towed on Saturday. On Wednesday the mechanic said he switched to the front tank and it starts and runs fine.
History: The truck is new to me. The fuel gauge is whacked. It reads way past full for rear tank and very low for the front tank. So I filled both of them. They both only took @ 10 galllons. I switched to the rear tank when leaving there. The engine quit less than a mile from the station. I switched back to the front tank and was able to get restarted and drive home. On Saturday I was driving (on the front tank) and it quit and I was not able to restart. I changed the fuel filter (existing one looked new, and was full of fuel, but worth a try). Wouldn't start. Out of options I switched to the rear tank. Still nothing. Called for a tow.
Now it's running and the mechanic didn't do anything other than switch to the front tank.
I should note that I had climbed a fairly steep hill about 1/4 mile before it quit. But both tanks are nearly full.
Any ideas to try? Or am I gonna have to pull the bed off and mess with these tanks?

 

[gnathv]

You probably have crud from deteriorated fuel pickups in tanks. Mine would starve and die then start after 15 or 20 minutes. Check fuel pressure at filter head from both tanks. Blow air through the fuel line back to the tank, (15lbs normally works) switch tanks so your blowing out lines to both tanks. Check fuel pressure again and see if it’s improved, if it is you need to clean out your tanks. I’ve had to do this on my idi and my powerstroke. If your tanks are full it will blow fuel out of the fill necks if the fuel caps are off, keep the fuel caps on and don’t over pressurize your tank.

 

[Big Bart]

Seems like goofing with the fuel tank selector is the root of the cause. Test you are getting power to the fuel tank selector valve. If so replace your fuel tank selector valve. They are getting old and start to stick, then can get stuck between tanks and cause issues. Also blow out the lines coming from the tanks in case they are slightly clogged. Not with 150psi out of your compressor more like 10-15psi.

If that does work check the fuel lines for leaks and test your lift pump pressure.

Let us know how it goes.

 

[quickster]

When my tanks were full of rust particles it would run for ten minutes, then start acting up before it died. did you dump the fuel filter to see what was in it? Put a coffee filter over a jar and dump it in. If you have what looks like mud color silt , and it doen't need to be alot, It's time to change the tanks. They are cheap, and you can do the sending units while you're at it. Bite the bullet when you pull the bed off. You only want to do this once. And if the tank always reads full, iirc that's a bad ground.
Cleaning tanks is a big waste of time, so don't even think of it.

 

[Brian VT]

Update after having it towed and then it started fine for the mechanic:

Over the phone me and the mechanic both decided that the tank switch valve was the culprit of the air leak and probably the fuel starve problem also so I had him bypass that valve and I picked it up.
It started with only 6 seconds of manual glow pug (it's 35 deg. here) and it didn't do the smoke show it had been doing at startup. Cool. Then it drove fine other than some random slight "surges". So I stopped for beer. Then driving home and only 5 minutes from my house, going up a slight hill, it quit. Can't get it restarted.
I guess the fuel pickup/sending unit must be all crapped? So I guess I'm gonna have to buy new tanks and sending units and switch valve and all that crap and take the focking bed off.
Happy Thanksgiving.

 

[quickster]

Now pull the filter and pour it thru a coffee filter. See if it has any ***** in it. And you don't know if the fsv is bad or not. You can feell for it on the frame rail with one hand and toggle the switch with the other. If you can feel a good snap when you toggle the switch from front to back it isn't the valve. If the filter gets enough crap in it, it will stumble then die. And another thing, notice how full the filter is. If it is anything less than full , then it's draining back. You got air.

 

[Brian VT]

Will do. Thank you.
Any tips on how to maybe get it running in the morning so I can drive it 3 miles home rather than trying to get it towed on Thanksgiving Day or have it sit there for another day & night?