Jeepdude_Jay

First a little history. I am a newbie here and have been searching a lot here over the last 2 weeks. I have learned a ton already.
I bought a 93 CTD, AT, 4x4, club cab, 148,000 miles, last week . This is my first diesel. It has problems shifting into OD, which is no surprise, I know. I narrowed it down to the TPS. Went to test it and thought it was bad. Tried to adjust it for fun and then discovered the real problem. With the TPS unbolted I can turn it by hand and get good readings on the voltmeter. The problem is in the hex drive setup that actually turns the TPS. The plastic shaft under the TPS has a small bolt that the head is rounded off. Also the hex socket the little bolt head fits into is worn. Replacing the bolt looks to be no problem but is the hex pocket it sets into replaceable without tearing down the injector pump?

12valve@heart

First of all, welcome to the world of Cummins and to DTR. As you're already discovered, there is a wealth of information hidden in these forums.

Now for your question, I honestly have no idea on a fix for your problem with the hex but if no one else chimes in pretty soon, I'd suggest that you contact Piers or one of the other site vendors that work on pumps. They may be your best source for information on this.

http://www.piersdiesel.com/

Sorry that I couldn't be of more help.

Jeepdude_Jay

Well that's a start. And thanks for the welcome. Anyone have any experience with this problem?

Bushy

You should have no problem getting that part. It is an 8mm (?) allen cap screw. Any Bosch shop will have one or can get one.
You can carefully remove the old one, and install the new one with little trouble.
While your at it, measure the amount of hex bolt protrusion from the bottom of the TPS body and replace that too.
When you thread in the new bolt just use some low test loctite on it once you have your protrusion right.

bob....

Jeepdude_Jay

Cool. That's what I was hoping. I am going to start by relacing the little bolt and see what that gets me. Do you know if it's metric? Just at a quick glance I thought it was #10-32 but it could be metric also. Anybody have a nice diagram of the allen cap screw part of the pump so I know what I'm getting into? I know there's a fair size spring under it.

Jeepdude_Jay

Well, I replaced 3 parts on the top of the pump. The part numbers below are BOSCH.

plate 1 461 901 489 $48.55
spring 1 464 651 430 $13.75
nut 1 460 363 300 $45.55
total after tax $116.37

They were pretty straightforward swap in/out. I have pictures in my gallery. The only thing they couldn't sell me was the small bolt screwed into the bottom of the TPS. They said it comes with a new TPS, from the dealer. I tried a new one from the hardware store but the head size is just slightly different, about .010 smaller hex size.
Now I get good voltage readings from the TPS when moving the throttle. I have adjusted the base voltage all the way from .26 to 1.26 and still can't get the OD to kick in right. Whether I drive it easy or hard I get no OD until I let off the throttle, say when coming to a stop sign, then when my speed gets down to 40 or 50 mph it kicks in for about a second then right back out. Occasionally in town it will kick in for a couple seconds then right back out again.
What's up? I have read a little about TV cable adjustment but I don't really understand what it does. Is it like a kickdown or what?

Jeepdude_Jay

Anybody have any suggestions on what to look at next? I still have no OD until I let off the throttle, and then only for about a second or 2. The TPS seems to be working correctly. I can't see how the speed sensor can be bad because the speedo works fine.

Den

1) I'd check the trans temp switch in the line. It should ohm out to 0 and only be an open circuit above 278 deg. If the computer thinks it's too hot, it won't allow it to shift into 4th

2) Coolant temp switch (left rear of engine) should ohm as an open circuit above 60 deg F. This will stop shifts into F because it thinks it's to cold

3) Inside the trans pan on the valve body is a soleniod for the 3-4 shift. There is a connector of the outside of the trans. You'll see the nuetral switch plug and then above that on the main case of the trans you'll see anohter connector with 2 wires. That is the overdrive solenoid connector. This should ohm 0 (closed ) showing the circuit is complete and the solenoids coil is ok. The nuetral safety switch can also be faulty.

4) All throttle linkage should be set first. TPS voltage should be about 1 volt or slightly above while resting on the low idle speed screw. When the throttle is wide open it should be at least 2.25 volts HIGHER than the output voltage at closed throttle. I can't find it, but I'm almost sure I read that if the computer thinks throttle postion is above 70% it will prevent the 3-4 shift. Which sounds like it could be your back off the throttle and it engages problem.

Personally I'd drop the trans pan an clean it. Change the filter, check the mounting of the overdrive solenoid, fresh filter and fluid and go from there. Can't hurt to service the trans and make sure your starting with good fluid conditions.


Den

ChrisLib

Mine was dropping out on the hiway, I ran new wires from the TPS to the computer using shielded cable, havent had any problems since, I think it has somethig to do with current induction from the alternator wiring in the harnes, wich causes a "dirty" signal for the TPS.