Replace Injection Pump?

[jerry598]

Have been living with the DTC 35/36 trouble code for thousands of miles now. Only driveability issue is with the cruise control which shuts off when the SES light blinks on. I've tried everything else, like replacing the lift pump, relocating the PMD under the front bumper, swapping out the PMD, rechecking all of the grounds, new fuel filter, gallons of diesel-clean, etc. I'm thinking it must be optical sensor.

Except for that, the truck runs better than new. After installing Heath's recommended chip upgrage 5 years ago, it starts quickly with little or no smoke and runs in all kinds of weather better than ever before.

What would you do? Should I leave well-enough alone or do an expensive pump replacement? Is there any other reason to change out the pump other than to have cruise control?

[Robyn]

That's a tough call.

The 35/36 code is all related to the pulse width signal from the fuel solenoid.

Likely not the optical sensor. Those usually set a 17 (High resolution fault)

The solenoid operates very fast inside the pump as it regulates fuel flow to the pump plungers.

If the computer does not see the expected return signal it sets the code (ses)

Have you tried adding a real good lube to the fuel to see if the incidence of the 35/36 setting changes ????


A slightly sticky fuel solenoid or a little wear in the thing causing fluctuations that fall outside the parameters in the computer programing will/do/can cause the error codes.

If you have not tried some lube, if it were me I would dump in a couple quarts of good old Tranny red juice.

There are lottsa fancy fuel treatments out there, but good old tranny oil will do the trick.

If some lube helps slow down the incidence of the codes popping up you will then know what it is.

The other possibility is that the ECM (COMPUTER) has an issue.

You might want to beg borrow or steal another ECM and try it and see if the issue follows or goes away.

Even a stock ECM will let you test and see if the issue is the IP or in the ECM itself.

If these tests reveal no change then comes the time to make the tough call.

It would be a real beotch to replace the IP and then have the same code show up again.

My gut feeling since you are not having driveability issues is that the solenoid response is just barely outside the spec.

PMD's can set 35/36 but it is rare to catch it, as normally the engine dies before the code can set.


Good luck and keep us in the loop.

[jerry598]

Thanks for the advice, Robyn!

The only lube I've tried is the blue 2-cycle engine oil, routinely a pint per tank with no change in symptons. I'll give some tranny fluid a try. I've got some left-over full synthetic tranny fluid on hand, would that be safe?

I'll see if I can get hold of a spare ECM someplace too. Thanks again!

[Robyn]

A pint is pretty thin.

Dump in a couple quarts of tranny oil when ya fill the beast.

Back when I had the big rig with the 500 Cat I used to dump in a couple gallons of tranny oil in each tank twice a year to keep the injectors spiffy clean.

More often if I was forced to use BIO FUEL

That stuff was on Cats list to avoid if possible.

[Dvldog8793]

Howdy
A pint per tank is not much, might be good for adding a little to the dry fuel we have but probably not enough to make the difference Robyn is talking about.
About twice a year I use 2-3 quarts of tcw3 rated 2 stroke oil. It has high detergent and is designed to burn in engines. That's what its for, cleaning and super lubing internal combustion engines. I try to find some that is clear or not dark color. It might just be my imagination but I think the trucks run stronger on that tank.
Every tank gets a 1qt mixture of cleaner/lube and 2stroke.
Good luck!

[rustyk]

As a recovering fuels and lube engineer, I agree that tranny fluid should be avoided. The TCW-3 2-cycle oil is a better choice, as it's designed to be burned; ATF is not.