You might want to consider just putting a new injection pump on the thing. I have been through everything you are currently dealing with and eventually that was the cure. I did the optic sensor and the stepper motor and 2 PMD'S and still had codes, hard starting and stalling. Rebuilt pumps are expensive, but I bought one from Peninsula diesel in Florida and it is working just fine. You do get what you pay for and they only rebuild them in so far as to get everything working properly and in spec, so not guaranteed that it is a new pump but certainly it will be a working pump. My son is driving this 65 and it has been completely trouble-free in the year since we put the new pump on.
Air in the fuel is always a concern so be sure you eliminate that possibility. I replaced every single rubber line and also one of the hard lines back to the tank which appeared to be rusting through. All of this stuff is very cheap and mostly just sweat equity, although the pump was I think $700 or something so a short-term pain but worth it in the end.
If you do choose to replace the optic sensor, you don't need to do any timing if you are careful. Use a feeler gauge to measure exactly where the old one is located, make some scribe marks and get the new one in exactly the same spot. It will be close enough that timing will not be required.
One last thing, crawl under and ensure the starter is torqued correctly and has the bracket attached that bolts it to the block. Backyard mechanics rarely take the time to install the starter correctly, and the result is broken bolts or a cracked bell housing which is a nightmare you do not want to visit. There is one of these trucks on my local Facebook marketplace right now and he has welded the starter on after he botched the replacement.
In reply to A 401 CJ :
It makes me think of lope tunes too lol
The black does work if wasn't done so poorly. If I was going to change the color I would have trouble not going white though.
In reply to bearmtnmartin (Forum Supporter) :
If I'm going to replace the optic sensor it does almost make sense to just do the pump. Taking the hit on the cost doesn't encourage me to take that route but I might just be putting off the inevitable. I think I will eventually just do all the fuel lines with hose. There's at least one fuel leak.
I did check the starter has the bracket. I should torque the bolts just to be sure. Cracking a block because the starter isn't installed correctly would be a real bad day.
Had a busy holiday so not much progress on the truck. Had some air in fuel issue or just ran out of fuel. Not sure, gauge showed 1/8 of a tank and it died. Struggled to prime it for a while and then, right when I decided to just pull the clear fuel lines a previous owner had installed and replace them with push lock AN hoses, the truck primed and idled fine for a few minutes after pulling it into the shop.
I was committed to doing the push lock hoses. The existing lines were leaking in one place at least. So dropped the tank and started that. I checked the inside of the tank and discovered there was no fuel strainer sock on the sender at all. The sender does look to be in great shape though. Luckily I had ordered a new fuel sock and installed that. I started making hoses and finished the tank to lift pump hose. Then I started pulling everything off the top of the engine. I discovered a mouse nest under the intake manifold.
Was hopeful that that was causing my optical sensor issues but when I pulled the wiring harness in the valley and traced the wires, it actually looked great with no apparent issues in the wires or the connectors. So I wrapped that back up.
Cleaned the mess in the valley out at least.
Going to continue building the rest of the hoses.
Any suggestions for things to check while the intake manifold out would be appreciated. Also suggestions for priming what will be a completely dry fuel system also appreciated.
Finished the fuel feed and return hoses with -6 AN push lock hose. Looks great. Probably too nice for this truck. Hopefully it helps anyway.
Next I'm going to try prime the system and check for leaks before I put everything back together.
Had a few minutes to prime the fuel system last night. Encouraged because it primed much easier than before the new lines and nothing was leaking. Hopefully start putting the mess together tonight.
Fingers crossed it's all tight and dry. I don't know anything about those to help but glad you're making good progress!
Love it. Continue to keep us posted.
Keep us posted. Also toss some fuel cleaner of your choice in, cheap insurance.
Thanks for the support.
Good news for this one. I put everything in the engine bay together but put off driving the truck because I was nervous it was going to strand me again. So I pulled the dash apart to try fix the broken odometer. The odometer was broken beyond repair.
So I found someone parting out a Tahoe and grabbed the gauge cluster and a few other pieces. Because the cluster I got was the later one and not for a diesel, I pulled the odometer cluster out and spun it up to match my trucks mileage.
Added LED bulbs, tried a new bulb for the glow plug light, and put it back together. It was late and I still didn't want to start the truck so I swapped the CDR valve out. Some say that its one of the more important maintenance items and it can't hurt.
And yesterday I finally sucked it up and drove it to get fuel. Started and drove great. Had no issues. And the glow plug light was really just the bulb so that's fixed too.
I also got the cigarette lighter working so I can actually use my FM transmitter. Another small win.
Unfortunately, I do always lose some. The odometer still doesn't work. Maybe the little motor is broke. And I'm an idiot and didn't look up how to disassemble the gauge cluster so I thought the needles had to come off to get the guage face off... so those are all messed up now. Got the speedometer, tach, and voltage to work somewhat accurately but the others are not. Something else to figure out.
Atleast you got some wins! Always makes it better.
In reply to Professor_Brap (Forum Supporter) :
For sure! And definitely feels good to not have a "dead" vehicle sitting in the shop anymore
In reply to white_averson :
I feel that in my soul.
Drove the truck to work after lunch. Decided to plug the optical sensor in because some people reported codes due to air in the fuel system. Surprisingly it started right up which it hasn't without the optical sensor unplugged recently. It even momentarily didn't have a check engine light. After a couple minutes the check engine light came back on and the truck was randomly stuttering at idle. I'll have to check the codes and see if I can figure it out. Still have the fall back of just unplugging the optical sensor again.
Drove the truck back from work. At idle it stutters, its actually like its getting too much fuel. Puffs of black smoke come out the exhaust with each stutter. Checked the codes and currently have DTC 17, 18, 35, 43, and 88. 43 is new and indicates low fuel temperature. But the fuel temperature sensor is part of the optical sensor that is causing 17 and 18 and seems directly related to the idle issues. Really seems like the optical sensor is causing the problems but do I want to spend $300 to find out or just suck it up and get a new injection pump for even more?
white_averson said:
Drove the truck back from work. At idle it stutters, its actually like its getting too much fuel. Puffs of black smoke come out the exhaust with each stutter. Checked the codes and currently have DTC 17, 18, 35, 43, and 88. 43 is new and indicates low fuel temperature. But the fuel temperature sensor is part of the optical sensor that is causing 17 and 18 and seems directly related to the idle issues. Really seems like the optical sensor is causing the problems but do I want to spend $300 to find out or just suck it up and get a new injection pump for even more?
Forgive me if this might be a super dumb question, but if it's just a sensor, it should be returnable if it turns out to not be the culprit, no?
In reply to golfduke :
You know what, I might be the dumb one. The sensor is such a specialized part, I just figured there wasn't a chance that I could return it. The sellers I can find have a 30 day return policy but then make it sound like it doesn't apply once its been installed. I mean, I assume I can clean the fuel off and it will appear to be "new and in unopened and unused condition" but that feels dishonest.
Nothing terribly exciting recently. Finally have a working odometer after sacrificing the second gauge cluster. Unfortunately it seems to be at the loss of my fuel gauge. It at least moved with fuel level before but now its stopped. So both my coolant temp and fuel gauge don't work. Considering pulling the motors from my donor clusters to see if that fixes them.
The truck stopped running with the optical sensor plugged in again. So I'm driving it with it unplugged. Confirmed that I have the weird '94 only 5068 injection pump so my options for new pumps is limited. Decided to gamble and ordered a used pump body with an optical sensor for cheap. I'll try that optical sensor and take the loss and assume the injection pump is my culprit if it doesn't work. I did confirm I have 5V and ground to the appropriate pins on the optical but didn't check the ECU pin for the output. Hoping the truck will drive for a few days without issues so I can finally knock out the clutch and oil pan gasket on my 128i.
In reply to white_averson :
Did you get this truck figured out? I'm having the same issue wondering if it's the optical sensor or something else?
In reply to Chancegoodridge :
Funny you ask, its been sitting while I dealt with other projects and I keep thinking I should try that sensor. With it being dark when I get out of work now, I'm even less excited to work on it in the cold. Hopefully I'll try it before snow hits. Then I have to deal with the transmission that fried reverse in our big snow storm last year...
Hope the truck is still running!
