NO HPCA

[450]

OK, I've done a search and came up with some info, but not for what I have. Recently replaced my motor with a used jasper rebuild, (ebay score on a whole truck) was told there was only about 18,000 on the motor and what I assume to be a rebuilt IP with it. The truck starts fine but has a slight lope at idle, goes away with minor acceleration. The HPCA would not energize so I took the top of the pump off, couldn't get the solenoid to activate with a hot lead so replaced it with a spare top from another pump, which would activate, but now there is no change in the idle when a hot wire is connected to the HPCA, which is the same problem I had when I started. Is there something else that effects if the HPCA activates to increase the timing when cold?

[NH2112]

Did you check the fast idle solenoid's function as well? It's attached to the throttle cable bracket and should engage when energized with a hot lead. It may need to be adjusted as well, which is done by turning the screw coming out of the top.

[450]

Yep, fast idle solonoid works fine, kicks down after it warms up, just don't seem to see any difference with the HPCA when it should be activating, even when I run a hot lead to it. Checked and cleaned the return check valve and it appears OK.

[john8662]

The HPCA solenoid in the pump will change the housing pressure that cause the pump timing to be advanced. You won't notice a better idle using the HPCA, although an engine usually runs smoother just after the initial start thant does after it's fully warmed up.

Anyways, you'll know the HPCA is working because the engine will have more of a "powerstroke" sound to it, it will have more diesel knock. The engine will be sharper sounding, etc.

For a rough idle situation, you'll need to look at a few places.

Make sure you have changed your fuel filter(s).
Check all line connections on the injection pump to be tight
Check all line connection at the injectors to be tight
Check all rubber connections on the engine an fuel filter housings.

Basically, you're looking for places where air can get into the fuel system, which will allow the engine to run rough.

[BobND]

If you take the return fitting/housing pressure regulator out of the pump top, and look inside, there should be a spring-loaded glass ball in there. Inside the hole where the fitting came out of, there will be a little pin. When the HPCA solenoid is activated, the pin rises up, and lifts the glass ball off it's seat.

If someone has removed the glass ball from the fitting, or the pin is not rising up when the solenoid os activated, there will be no change in housing pressure, and no change in the diesel sound abd timing when the HPCA is activated.

[Portland Suburban]

HPCA? Help out a newb here. smile.gif

[450]

Thanks BobND, that was my thought too so I checked it and made sure that it still had the spring and was not plugged, may change it out with another I have to check for sure, Just not getting the "powerstroke" sound when Its cold or if I run a hot lead to it, making me wonder if the timing is already too advanced. The timing lines are aligned, but thats the way I got it, tried bumping it up a lineswidth, but felt that it sounded like too much, so I put it back. John8662, went the checking for air route, no bubbles in my clear return line, not so much worried about the lope at idle, motor has been sitting awhile, need to put it to work to see if it cleans up alittle, rebuilt injectors, new filters and rubber lines. Portland, the HPCA is a solonoid that raises the pump housing pressure that causes a temporary increase in timing, which aids engine running when cold. Its on the left of the pump (when looking at the mounting flange) and has a green wire going to it. Thats kinda in laymans terms, I'm sure others more familar with it can get more detailed.

[BobND]

450,

Just for the record, the HPCA solenoid LOWERS housing pressure to cause the timing to advance.

If you are not getting a change in diesel rattle as you activate and deactivate the HPCA solenoid, the advance piston at the bottom of the IP may be scored, worn, or stuck.

With the engine idling, move the hinged lever at the RH side of the pump so as to depress the pin operated by it's lower end. As the pin is pushed in, timing is retarded, and you should notice a decrease in rattle, and then smokey exhaust, from the late timing. If this seems to work, the advance piston is working, at least to some degree.

[twaddle]

Before you strip anything out, also test the pump by pushing the external lever at the side of the pump with a long screwdriver.
This should change the timing as well.
The piston at the bottom of the pump may be siezed giving the same symptoms that you would get if the electrical HPCA was at fault.

Jim Twaddle
Biggar, Scotland

[450]

BobND
Brain cramp on my part, thanks for catching it, backwards thinking on my part. Anyway, the advance piston seems to be working, I checked it before I began the post as you suggested, it does seem to retard the timing when pushed in, haven't driven it much since getting the motor in, think I'll put a few miles on it to see if it clears some.