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Discussion Starter · #1 ·
We're finishing the installation of a NOS 4bd1 (ass'y 12/'79) into '74 GMC 4x4. The last wiring hookup is to the alternator/external voltage regulator. I haven't been able to find a diagram in any of my manuals or search in the forum. The regulator that came with the re-power unit does not match the plug on the alternator, which has three wires, plus charge terminal. Anybody have any help?

Also, we're having truouble priming the injector pump. We've primed through the filter assembly, at the pump, and the bleed valve on the pump with clear fuel. There are occasional tiny spurts to be seen, but not the flow I'm expecting from all other Isuzu's we've used. Is the long dry time contributing to dried out seals and leaks? What should we look for? The inside of a pump is the only thing I've never attempted, but not afraid to try.
 

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isuzufarmer,
I have info on the terminal connections for the original alternator of similar vintage (1980), but I cannot get it for you until tomorrow evening. It's at the job, and I have an out of town job first thing in the morning. If no one else offers it up before then, I will post tomorrow evening. (We used an early Delco regulator, and then later a mechanical Motorcraft regulator, both worked fine with the Isuzu alternator.)

On the fuel problem, have you cleaned/removed the strainer in the inlet? It is just a small nylon "whistle" shaped obstruction, can be removed if your filtration before it is sound.

Be careful on initial startup, after a long sit, mine "ran away" on initial startup, had to put my hand over intake a few times til it calmed down.

Good luck,

Terry
 

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Coog,
Really not that intense....besides, I really didn't want to break the motor, it went wayyyyy past governor real fast. Luckily I started it while near the front, and my Cummins inlet was accessible.

Terry
 

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Discussion Starter · #5 ·
Terry,
Thanks for the info. We'll watch out for the runaway! BTW, we have an Isuzu regulator, but it doesn't have the same plug configuration as the alternator, there are 4 leads in the regulator plug, 3 in the alternator plug.

Where is the screen you reference? Do you mean in the inlet tube before it goes to the filter assembly, or inlet into the injection pump? This is something I'm not aware of. Is there any chance a leak in the priming pump could be causing the fuel priming problem?

Tim
 

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All the Isuzu diesel alternators that I have seen had internal regulators. You can't use an external regulator with an alternator that already has an internal regulator without significantly modifying the alternator. Typically, alternators with more than two connections (one being the big wire that goes to the battery) have internal regulators. Post a picture of the back of your alternator and someone may be able to help.
 

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ASTR,
The alternators of 1980 vintage used an external regulator and were available in 12 or 24 volts. The alternator used a pigtail coming out of the case with a 3 terminal plug on the end. The 3 terminals were arranged in two layouts which will be discussed later.

Isuzufarmer,
The screen I am referring to is inside the inlet fitting of the LIFT Pump, to catch large debris, but can be rendered plugged easily.

All,
Find attached a crude JPG of the alternator plug. We found two sources of layout for this plug in supporting Isuzu manuals. The key is to find the "E" terminal as it should Ohm directly to ground. The "F" terminal always seems to be in the same place. The "N" (stator) will be the one that is left. "E" to "F" should be approx. 19ohms (for 24vdc) and probably approx. half that for 12vdc. Check for proper ID with an ohmeter before attaching real power.

Terry

Will try to post JPG again as manage attachments has probably timed out.
 

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Discussion Starter · #9 ·
Thanks for everyone's help and suggestions. We did find a supplemental engine manual, with electrical diagrams that look like they should help us sort it out. Again, many thanks.
Tim
 

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Discussion Starter · #10 ·
BTW, after nearly a day's struggle attempting IP priming, we threw up our hands and pulled the pump off to take to repair shop. There was some really skanky fuel in it, and we were never able to get it to move any significant fuel, or give us a pulse to any injector. It still looks brand new (which it is), but must either have some residue in it, or failed seals or O-rings. The priming pump leaked substantially while attempting the prime, which is probably symptomatic of dried-up seals, etc from a 30-odd year old new engine. When I find out, I'll update.
 
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