Well, well, guess what.....My fault, I didnt check to see if the alternator had any A/C voltage. How was I suppose to know this??? So I have to pay for the 2 Bosch controlers (325.00) on the pumps they sent me plus 2 over night frieghts (200.00) Im out on the customers job 850.00. I lost my *** and I still have to put another pump on tomorrow and an alternator. ::((

 

Can you explain more to me? I'm having this same problem. The truck will idle very rough for about 5 seconds, then die. Over and over again. Just put a new VP44 in and everything else has been checking out. No codes, no bad grounds, good lift pump pressure, but she still won't run and the go peddle does nothing. Please tell me what you did to fix this.

 

What would ac voltage have to do with the pump? Or is it that the alternator's output was not being rectified or chopped?
I am curious as to what damage this will do to the ip as i want to protect mine at all costs.

 

Place a volt meter on A/C current and place the positive on the back of the Alt where the cable runs out of it to the batterys and the other end of the meter on the battery ground. Mine showed 27.0 A/C volts. When talking to the guy at Industrial he said everyone knows to do this.. I havent ever heard of this kind of a test ever. ((((Scratching my head))))

 

I have never heard of it either. Question, did it solve your problem?

 

Well, here I am with a new alternater on the truck and I still get 27 volts of A/C. So I test all the other trucks in my shop and guess what,,,, they all have some where around 27.0 and 26.8 of A/C. Thats Dodges and Chevys.. Is industrial blowin smoke up my but or what??

 

lol, sounds like a load of crap to me.

 

There is no way to get 27 volts AC if your alternator is working correctly. The alternator generates 3 phase AC voltage as shown in the top waveform. The black (1) red (2) and blue (3) are the 3 phases. There are 6 diodes that rectify the 3 phase waveform (or flip the bottom of the three waveforms up), see the lower waveform. The resultant DC out of the alternator (heavy lug terminal) is shown by the green at the top of the lower waveform. As you will see it is not perfectly flat and the ripple is a small level of AC voltage. If you have good batteries and clean connections, this ripple will not show up.

So to get 27 volts of AC, your alternator is bad with shorted diodes worn out brushes, or maybe you are misreading the DVM. In post 19 you said the DVM was on AC CURRENT. Did you mean to say that? It should be on AC VOLTS.

 

Good alternator should put out 12.5-14.5 volts!

 

I've always had problems starting anytime i open the feul system for anything. I couldnt even start after a new lift pump, VP44, and primed till fuel was coming out of injector lines.

The only thing that worked for me, and has worked every time is to find a big hill, roll start using the clutch (hope you have a stick)

This has alwaays worked even when the vp was shot. I dunno why but it works.

 

Go out to your truck with a volt meter set on A/C and measure from the charging post of the alt to and the other end on ground. Your going to see 27.0..Its a fact I tested 3 differnt diesels.

 

Jay, I just did mine, 14.8 VDC at the lug.

Are you sure your meter is reading correctly?

 

I just measured mine. It reads 0.037 volts AC at the lug.

The heavy lug, at the alternator is connected to the PDC and then to the driver’s side battery through the 140 amp Gen. fuse in the PDC. Are you making the AC measurement with the wire disconnected from the alternator or is the 140 amp fuse blown? These may cause the AC voltage you are seeing.

 

this makes no sense what so ever...

if your old VP44 works and new one is dead?

it's a normal diagnostic procedure to replace a part with a known to be good unit.

have always thought output terminate of Alternator puts out DC voltage (13.5-14.2 range). however Alternator originally puts out AC voltage, which is converted to DC.

 

---->ACV<--- from the lug on the back of alternator and the other end on the battery ground 27.0. All trucks read the same here in the shop. If I check DC volts I get 12.8