1990 7.3 Engine run problem - Diesel Forum

DUMBnEASY · 02-13-2008, 01:07 AM

I have a 1990 7.3 in an old U-Haul 17 ft. E-350. It just now has 200K on it and has been a very dependable vehicle with the exception of the tranny's 2nd gear in this old C-6. But 2nd is so short I haven't missed it.
I live in Lincoln, MT which is very cold and snowy this time of year, so working on my truck is problem. Further, I am in high altitude at 4600 ft. and to go to town, which is Helena, I must cross the continental divide 7200 ft. Round trip is 110 miles.
My first indication of problems was while pulling out of Home Depot in Helena. I pulled out into an intersection and my truck just quit. It took six tries at cranking to get it to start again.
Finally it did and I continued on my way without incident...until I started climbing the divide. As I neared the top it started to miss and attempted to die out, but when decelerating, not accelerating. It did that a couple of times but I made it home.
I replaced the fuel filter and because I'd seen slight fuel wetness around my mechanical fuel pump, changed it as well. I had also previously (within a couple thousand miles) replaced all the glow plugs.
I use a strip heater in the winter time, and my truck will start right up even at minus 20. However, a couple things, my glow plug light never lights, and that relay has recently been changed as well, but it just never lights even though the engine fires right up.
My problem now is not that my truck doesn't start, my problem is that unless I baby the gas pedal to slowly ease off the accelerator, the engine will die instead of idle.
I took it out on the road two days ago and it started fine, and with my foot on the gas to keep it from dying it gets going right up to 65MPH with no problem as long as I keep my foot on the pedal. However, as soon as I ease up on the pedal the engine wants to die, so it's constant coordination between brake and gas pedal to slow down and keep running.
And, in reverse, I get a continual lerch when backing up and having to use brake and pedal.

If someone has a clue I could sure use a little help. I have factory manuals and electrical and vacuum books. I'm thinking it might have something to do with lost vacuum, but I have incidents of folks saying something about a CPS?

Anyway, whadaya think?

Thank you

Steve in Lincoln

cdnsarguy · 02-13-2008, 06:10 AM

Read my reply to the E350 post above...... do the fuel pump test.

Check the WTS wire.....

Quote:

replaced all the glow plugs

What brand...........

Do you use fuel additives......... did you fill with fuel just before this problem occurred, if so check for gasoline in your fuel.

88beast · 02-13-2008, 07:44 AM

the lerch is a bad engine or tranny mount mine does the same thats what we narrowed it down to
is the idle set right since its high altitude raise the idle some to keep it going
dying on deceleration could be the fuel its self not prepared for that height look into additives

you may need to do a ram air intake to keep the air flowing to the motor with thin air and it being colder the engine will struggle more (proper warm ups will help)

good part is it dont seem like an internal thing i think its your location
did it drive well on the test drive?

LMJD · 02-13-2008, 07:59 AM

Quote:

unless I baby the gas pedal to slowly ease off the accelerator, the engine will die instead of idle.

That's usually a metering spool valve hanging up in the idle circuit. The problem can be a bit of crud or the valve and bore are scored just due to old age and lots of miles and the valve hangs up in it's bore.
[quote][is the idle set right since its high altitude raise the idle some to keep it going
dying on deceleration could be the fuel its self not prepared for that height look into additives /QUOTE]
As you probably already know, altitude has nothing to do with fuel or your problem. I can't remember about Helena, but there's a good authorized Stanadyne pump shop in Billings if worse comes to worse.

Quote:

I live in Lincoln, MT which is very cold and snowy this time of year

Yea, last time I went through Unabomber country there was lots of white stuff on the ground!

DUMBnEASY · 02-13-2008, 02:06 PM

I want to thank you folks for your guidance into my problem. In seeing your responses I need to add a few things.
1. This truck used to run flawlessly here in Lincoln altitude and all.
2. Motor mounts are OK and the lerching is in engine speed.
3. I like the stuck governor-new non-lubricating diesel fuel theory.
4. The additive I use is a product called Sea Foam but I only started using it after the initial problem (stalling in the intersection) occurred. It is what my local mechanic recommended.

Thank you

Steve in Lincoln

DUMBnEASY · 02-14-2008, 02:04 AM

OK, no one has said another thing.... So I have another question. First, cost is not the issue here. I need my truck!!!

So, you know I have new filters, new injectors/glow plugs, and plug heater relay, mechanical fuel pump, etc.

So what else is there to replace to fix my problems. Injection pump, return line(?), and sensors? If I replace these things will it run?

I really really want my truck back and I'm getting really really desperate!!!!!

DUMBnEASY · 02-14-2008, 02:07 AM

CDNSARGUY....H-What is a WTS wire?

DUMBnEASY · 02-14-2008, 02:13 AM

[quote=LMJD;1506504]That's usually a metering spool valve hanging up in the idle circuit. The problem can be a bit of crud or the valve and bore are scored just due to old age and lots of miles and the valve hangs up in it's bore.

Quote:

[is the idle set right since its high altitude raise the idle some to keep it going
dying on deceleration could be the fuel its self not prepared for that height look into additives /QUOTE]
As you probably already know, altitude has nothing to do with fuel or your problem. I can't remember about Helena, but there's a good authorized Stanadyne pump shop in Billings if worse comes to worse.

Yea, last time I went through Unabomber country there was lots of white stuff on the ground!

Greek is not in my vocabulary......and Metering spool valve is not in my 1990 Ford Truck Manual.

So........what is it, what does it look like, and where do I find it?

LMJD · 02-14-2008, 10:34 AM

Sorry I wasn't more clear. It's located internally in the injection pump, that's why I mentioned the injection shop. The pump has to be removed and repaired by that type specialty shop. But with that said, some of us here who have actually mis-spent the better part of our lives as truck mechanics don't presume to make an accurate diagnosis by staring at a computer monitor. Without leaning over your fender with the hood up for a few minutes, mine is just an educated guess. No way can I guarantee for sure that's your problem although it's highly likely. I was mainly trying to steer you away from the high altitude adjustment/fuel mis-information.

cdnsarguy · 02-14-2008, 10:53 AM

Wait to start light connector for the GPs, located on the firewall by the controller.

DUMBnEASY · 02-14-2008, 06:10 PM

Quote:

Originally Posted by LMJD

Sorry I wasn't more clear. It's located internally in the injection pump, that's why I mentioned the injection shop. The pump has to be removed and repaired by that type specialty shop. But with that said, some of us here who have actually mis-spent the better part of our lives as truck mechanics don't presume to make an accurate diagnosis by staring at a computer monitor. Without leaning over your fender with the hood up for a few minutes, mine is just an educated guess. No way can I guarantee for sure that's your problem although it's highly likely. I was mainly trying to steer you away from the high altitude adjustment/fuel mis-information.

Well thanks LMJD! However, as... "some of us here who have actually mis-spent the better part of our lives as truck mechanics don't presume to make an accurate diagnosis by staring at a computer monitor...." keep in mind that my shop is the outdoor world of snowed in Montana and as such...and with my lack of knowlege, the only place I should be for initial diagnosis is in front of my computer screen.

So....I'm thinking....because of the new fuel my governor could lack lubrication. And the metering spool valve. Both are in the injector pump-right? So it sounds like a new injector pump and while not certain, at least likely my problems go away.............YES?

To which you answer, "Yes Steve.....unless they don't go away." Right? LOL!

By the way...do the old 7.3 diesels like mine also have Cam Position Sensors? And of course they are differnt than the new ones....right?

Admit it... I'm getting good at this!

cdnsarguy · 02-15-2008, 02:40 AM

No CPS on IDI..... double dose the fuel with a diesel fuel additive see if there is any noticeable performance increase........

LMJD · 02-15-2008, 12:06 PM

Quote:

So....I'm thinking....because of the new fuel my governor could lack lubrication. And the metering spool valve.

That's always open for debate, personally I never add anything and never have any pump problems mainly because the refineries have been adding a lubricity additive even way back in '92 when they first cut down on the sulphur content.

Like posted already, you might try Power Service or whatever if the problem is a varnish buildup or a speck of foreign material. On the other hand, if the spool valve and bore are scored, no additive is going to smooth a rough sliding surface. Originally the valve and it's bore are smooth as glass with a very tight tolerance.

If you end up going the rebuilt pump route, you get a much better rebuild job by having a local fuel injection/turbo shop do the work rather than the "production line" rebuild type outfits that are always recommended here. The one our local diesel engine and truck repair shop owner uses for his pump work and highly recommends is Signature Fuel Systems in Billings, but I'd think you might have one in Helena too. Signature is an authorized Stanadyne dealer and repair shop. Our pumps are Stanadyne brand in case you didn't know.