I had topped off the batteries on the truck (if they are down even a little, it does

[jrsavoie]

I had topped off the batteries on the truck (if they are down even a little, it does not like to cooperate). She fired up with lots of smoke, white smoke. Let her even out, and took her down the road. Better, but not quite right though, hence the above questions.

I'd recomend some heavy duty battery cables. An auxilary alternator cable, and to check all of your glow plugs.

How long have the glow plugs been in? If for over 2 years I would pull them for a visual and recoat them with copper coat or some other good high temp anti-seez. I'd pull them regardless if you do not know if they were anti-seezed on the last install

 

[normburns]

Thanks for the ideas.
Batt cables. I have a 4 gauge from pos - pos. Should I also run an additional ground?
Aux Alt cable. If you could point me to a thread, I can handle this.
Glow plugs. Replaced last year, with the best I could find at OReilly Auto Parts.

The reason I am chasing voltage is because I have never heard the pump fire. The PMD helped a little. I wanted Leroy's Walbro LP, but being out of a regular paycheck for over 3 years has taken a toll on finances, so I bout a new AC/Delco for $55. It also helped a bit... BUT I HAVE NEVER HEARD THE PUMP FIRE. Until I hear that, I will be suspicious that it is not firing, for some reason.

I am no diesel mechanic, but I have been working on vehicles and things for 45 years now. As my knowledge of diesels grows (thank you forum members!), I will solve this problem.
Have a great day!

 

[jrsavoie]

Hope this is readable.
Mods feel free to edit and add the other brand of glow plug in.

Thanks for the ideas.
Batt cables. I have a 4 gauge from pos - pos. - Check out racedaymechanics battery cables. Cables like that make quite the difference in starting and are highly recomended. On some of our older trucks the cables suffer hidden interior corrosion, accentuating the fact that they are already undersized.

Should I also run an additional ground? - I run several aditional grounds. One from the battery to the battery box mounting bolt. That is to replace the lame screw to the fender ground. I run from the battery box ground to the ground by the starter. I also run from the battery/or ground cable on the intake to the stud near the firewall that all the little ground wires run to. I use a lot of coppercoat anti-seeze/neverseez & dialectric grease. I also add a ground from the heater blower to the dash support bolt right next to it.

Aux Alt cable. If you could point me to a thread, I can handle this. - Most often I use an OEM cable with the fusable link in it and run to the battery that does not currently have an alternator cable. You can double stack the cables on the alternator stud and still use the rubber cover. You can always add length if necessary. The OEM cables are undersized. Imagine that out of GM.

Glow plugs. Replaced last year, with the best I could find at OReilly Auto Parts. - I would check your glow system with a tester or 2 and a buddy. Pull the spade on the glow plug and test for continuity. One test lead to the glow plug spade and one to ground. While you are there and the spade is off the glow plug, test for continuity from the glow plug controller to the spade connector.
As far as I know there are only 2 good brands of glow plugs for these vehicles. I use Ac Delco 60G's.

Check the oil and coolant. You can't check them to much.

I also run at least 1/2 gallon of fuel out the drain into a gallon pickle jar. I let it sit and look for water bubbles or crud. I've actually had just that cure issues before.

The reason I am chasing voltage is because I have never heard the pump fire. The PMD helped a little. I wanted Leroy's Walbro LP, but being out of a regular paycheck for over 3 years has taken a toll on finances, so I bout a new AC/Delco for $55. It also helped a bit... BUT I HAVE NEVER HEARD THE PUMP FIRE. Until I hear that, I will be suspicious that it is not firing, for some reason.

I am no diesel mechanic, but I have been working on vehicles and things for 45 years now. As my knowledge of diesels grows (thank you forum members!), I will solve this problem.
Have a great day!

 

[JMJNet]

if it is a 94, based on the signature, I would suspect the OPS is not firing the LP when engine is running.

I would do the LP test when engine is running to eliminate possible OPS issue.

As for GP, I hope you are not using Autolite or Champion GPs.

 

[jrsavoie]

With the truck running. Check for voltage at the lift pump from the from the OPS/ Oil pressure Switch/oil pressure sending unit. If you have low voltage the OPS is definetely bad.

You can have voltage at the lift pump but not enough amps to run the lift pump. Which also means the OPS is bad. But you can work around that by doing the Double lift pump relay update. Which I recommend doing regardless. It's fairly cheap and definetly saves money in the long run. The voltage from the OPS should be enough to trigger the relay and your lift pump will run.

Do the lift pump test. Crack the Tee/drain valve with the truck running, If the truck dies your lift pump is not running

You can have voltage at the lift pump but not enough amps to run the lift pump.

 

[normburns]

With the truck running. Check for voltage at the lift pump from the from the OPS/ Oil pressure Switch/oil pressure sending unit. If you have low voltage the OPS is definetely bad.

You can have voltage at the lift pump but not enough amps to run the lift pump. Which also means the OPS is bad. But you can work around that by doing the Double lift pump relay update. Which I recommend doing regardless. It's fairly cheap and definetly saves money in the long run. The voltage from the OPS should be enough to trigger the relay and your lift pump will run.

Do the lift pump test. Crack the Tee/drain valve with the truck running, If the truck dies your lift pump is not running

You can have voltage at the lift pump but not enough amps to run the lift pump.

Yes, I suspected that could be an issue, having some voltage, but not enough amperage to do anything. Dual relay mod... without looking it up, I am guessing that is involves using the normal output trigger from the stock LP relay, to drive a second relay? I am looking at a couple of options on that line. I have a few of the Bosch relays, and I have a spare GM relay with a different p/n, but the same schematic and pinout as the stock LP relay. If I am willing to accept the limited risk of having fuel flow, with the engine not running (would not even consider it with a gas system), couldn't I just use a "key on" 12vdc source to trigger the relay? If I recall correctly, the purple wire from the relay feeds the power to the LP?

Can ANYONE should me a pic of this "T" in the fuel system? The only "t" I see is part of the cooling system. The only sort of a bleed I see for the fuel system, is the top of the filter. Thanks again for the info, because I really need to get the truck running right in the next few days... I need it to move a little crippled Bro about 25 miles, to a better/safer apartment.

 

[Paveltolz]

The "T" is to the left of the Oil Fill Tube in this picture.

 

[JMJNet]

It is called the t-valve since the opener is in a form of a "T". Just FYI.

I would suggest to spend a lot of time with the picture thread in the Technical Library to familiarize yourself with the engine of this truck.

Double relay mod:
http://www.thetruckstop.us/forum/showthread.php?4464-OPS-relay-install/page5

Post #63.

 

[jrsavoie]

The dual relay mod is as easy as anything. Buddy's schematic is so easy to follow, I was able to do it at least twice.

The 94's are even easier. You can access power and trigger juice from the OPS right at the lift pump fuse on the passenger side firewall.

If your OPS is putting out juice, it probably is putting out enough to trigger the relay. The other relay is triggered by the glow plug controller.