Just because when I get into one problem, I can't help but cause more...


I have a 1990 F350 with a 7.3L diesel and an automatic transmission. It is normally my daily driver and has always been stone cold reliable. Recently it started losing prime and I got stranded at the airport after coming home from a long work trip (I did eventually get it started after bleeding it, but had to get a jump). I traced that down to the lift pump and changed the lift pump.

For those of you who don't know, on a 6.9 or 7.3L diesel it is very easy to get the arm of the lift pump to go OVER the cam instead of under it. In fact, if the lift pump goes in easy, you did it wrong. It will bolt in like it's right at home if the lobe in the cam is down with the arm above the cam... it just will break the arm when you turn the engine over. You can figure out how I know this.


So, to stop this, I bumped the engine over a number of times until I was 100% positive that the arm was in the right position for the cam so I could install it. I left the key in the on position between bumping becasue, well, I figured that once the glow plugs went through a cycle once they wouldn't cycle again and I'd save battery power.

So I got everything back together and now my glow plugs won't stay on long enough to start. They should be staying on for at least 30 seconds at the temperatures I was in and they were staying on for 3-5 maybe (at least the glow plug light anyway). The truck did start after all this was done, but I'd had a heater under it so the short glow plug cycle time wasn't too unusual (and it started right up anyway). But NOW even with the cold weather the glow plugs are still not staying on.

The batteries ARE due to be replacement, but I've never noted a reduced glow plug cycling time with weak batteries before (when it's been extremely cold I'd be unable to turn it over before they would stop cycling, I've had the batteries on a charger between working on it and they are turning it over perfectly fine), next on my project list was to replace them with new batteries, but I was on the fence about whether to do that right away until I figure out what is going on with the glow plugs.

At the same time, I noted that my heater blower is only working on high. I want to think this could be related, but I can't find any wires I might have disconnected or broken under the hood or blown fuses under the dash. If it wasn't for that, I would have bought a new controller and glow plugs already, but I hate to do that to find out there was a fuse or wire somewhere blown or broken (or worse yet do it and it still not start and not be able to find the problem and still be out the money).

Temperatures in Alaska are going to be dropping below zero at night fairly soon, if they haven't already. I'm going to be home next week. My backup truck is an '85 250 with a 6.9, and it's low miles so it runs good, but I don't have it set up as good for extreme cold as the '90 350 (I started that truck at -50 last winter).

 

Possibly the relay behind the air cleaner for the glow plugs, that would be me first place to check, Next would be the connector where the glow plugs connect, should be a wide connecter on passenger fender with multiple wires, check to see if the glow plug wires have melted as that was my problem, cut them off then soldered to solve the issue.

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When was the last time you replaced your return lines? O-rings under the plastic tee's along with the tee's could be overdue.

 

Wide connector, passenger fender.... hmmm, that's where I was working too. I'll have to check that. Guess I'll hold off on ordering stuff until I take a closer look at all connectors over there.

Return lines and o rings replaced within the past few years, I think I replaced all those T's at the same time, I know I replaced everything including the T's on the '85 when I changed them this summer. I'd actually replaced the lift pump once before. We basically use jet fuel for diesel in Alaska though (at -50 untreated diesel doesn't gel). Don't have any signs of leakage from my Ts on this truck at least. Does it turn back and forth to rubber a couple times on the way to the tank as well? I should take a good look there too.

 

As far as having a leak goes, If you haven't already I would suggest ditching the tank selector valve and running off the main tank, every one I've seen has had problems with the valve. And if you haven't already ditch the dual piece fuel filter IE water separator screw on bottom, the seal always leaks. Go for a wix one-piece fuel filter, run about $40 but save the headache. A problematic hose I know of is the inlet rubber on the fuel pump, the hose can come lose from the metal line leading back to the tank.

 

Gald to see someone using and posting my input .. thanks D ..

I found several cracks in my EOM hard line from the tank switch to the lift pump ... prelace it with Gates Bio-Guard bio-diesel grade fuel line ... no porblems since in that area ....

 

Always wise to spread information that's valuable haha

 

I don't have any known leaks at this time, I really want to be able to use both tanks (actually, this truck is a crew cab so I seem to recall both tanks are supposed to be the same size, so which would be the main). I'd actually thought about eventually getting the larger tank to replace the rear (35 gallons IIRC). It'd be pretty annoying for me to go to one tank only, to be honest. I live in a semi rural area (it'd be considered very rural for most of you, but it's on the road system so it's not quite rural for Alaska). I do a lot of driving and it gives me a lot more options to have two tanks worth of fuel.

I might change to that one piece next time I change my fuel filter though, I'd thought about it before but never did it.

 

I see the main tank as the front, I bought one and kept the old in case of emergencies, the dual piece filter currently is sitting on the back of my truck waiting for something to happen haha, what part of Alaska are you from if you don't mind my asking

 

I live about 30 miles southeast of Fairbanks, look up Salcha, Alaska if you'd like.


I generally run the front first as well. I like to run the front to 1/4 then switch to the back. Fill when it gets to 1/4, gives me plenty of reserve between the two. If I ever get the larger rear tank, it'd be the primary though and used first... since it's twice the size.

Here's some eye candy for you as well, new farm truck...





Cummins NHC-250. 855 Cubic inches, or around 14 liters...

5 speed allison, sits over 10' tall. The pipe on the driver's side there is the air intake, it has the deep water fording kit on it.

 

Ohhhhhh pretty I have a buddy of mine from Kenai, and some other people I know from Alaska, not sure what part though, will have to ask them