Tach Problems

buffalofo

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Hey there I have a question pretty new to the idi world. I have a 1989 7.3 with an aftermarket turbo hooked up to a factory c6 3speed trans. My tach isn’t working and I’m trying to figure out where I should start. I am 99 percent sure the in cab tach is stock but my truck having the c6 it doesn’t have the tach sensor strapped to the IP. Everywhere I look everything refers to the tach sensor for the e40d on the injection pump but my truck doesn’t have that having the c6. Any clues on where I can start? Sometimes on start up it’ll jiggle a little up to 800 or 1000 rpm but never reads over that and once I start driving just sits dead at 0. Thanks for any input in advance!

-1989 F350 XLT Lariat 7.3 aftermarket turbo and c6 trans
 

Cubey

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Hey there I have a question pretty new to the idi world. I have a 1989 7.3 with an aftermarket turbo hooked up to a factory c6 3speed trans. My tach isn’t working and I’m trying to figure out where I should start. I am 99 percent sure the in cab tach is stock but my truck having the c6 it doesn’t have the tach sensor strapped to the IP. Everywhere I look everything refers to the tach sensor for the e40d on the injection pump but my truck doesn’t have that having the c6. Any clues on where I can start? Sometimes on start up it’ll jiggle a little up to 800 or 1000 rpm but never reads over that and once I start driving just sits dead at 0. Thanks for any input in advance!

-1989 F350 XLT Lariat 7.3 aftermarket turbo and c6 trans

This goes bad at the wires entering the sensor. It's not needed for C6 operation so it's only for informational purposes. My RV lacks the sensor entirely and has the port plugged, because Econolines didn't get tachs as an option until 1992. When they began partly switching to E4OD around 1989, they got the sensor for the trans, but still no tach. I'm guessing anyway. Dunno if IDI vans before 92 got E4OD.


It's not on the IP, but in front of it. This shows the plugged port for the sensor on my RV.

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buffalofo

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Hey there I have looked for the plugged port but it looks like mine lacks it entirely? I can attach a photo and maybe I’m just missing it? There is a connector with a wire going into the bottom that feeds into the cab but I figured that’s for the aftermarket oil pressure or water temp gauge.
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buffalofo

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Alright I think I may have figured out what the issue may be. For some reason I believe the previous owner had to swap out the IP and or the cover. When they replaced it they must have just used an older model cover that doesn’t have the sensor port and since it’s a c6 and doesn’t rely on that just let it be and let the stock wires dangle. Maybe it was when they were adding the aftermarket turbo? I’m going to try to track down the stock wiring connector and if that’s the case and it gets power than I may just buy a new/used IP cover that has the sensor port. Will update when I get it figured out.
 

Cubey

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When they replaced it they must have just used an older model cover that doesn’t have the sensor port and since it’s a c6 and doesn’t rely on that just let it be and let the stock wires dangle.

Yep. One or both years 83/84 lacked the port. My 85 RV has the plugged port, so it had to have been older than that. Another obvious thing is the oil filler. That's the old cam-on filler cap. Not sure when they switched to the plastic threaded cap with an angled filler neck, but my 87 has it:

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buffalofo

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Sweet, thank you for the input I appreciate it a lot. If I go to swap the cover do you have any advice on that? I’ve heard you have to be careful because the timing is linked into it somehow. Trying to decide if this is a job I can figure out or if I need to bite the bullet and go to a shop.
 

Cubey

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Sweet, thank you for the input I appreciate it a lot. If I go to swap the cover do you have any advice on that? I’ve heard you have to be careful because the timing is linked into it somehow. Trying to decide if this is a job I can figure out or if I need to bite the bullet and go to a shop.

I haven't messed with that, but I'm sure someone else will chime on.

Or you could just do without the tach. It's not really a requirement. These engines are governed, unless that was messed with by the past owner.

Or buy an aftermarket tach. It would probably cost less than buying the later cover, the tach sensor, and paying a shop to mess with that.

If it was me, I'd leave it alone and do without. I mean, I have no tach on my RV and it's fine. Spend the money on gauges that matter, like EGT, trans, etc.
 

Jesus Freak

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Yeah, you'll have to disconnect the IP from the timing gear and pull the cover straight up. If you're really careful and mark the IP position and don't let the gear jump a tooth, you'll be golden. I've done it. I disconnected the fuel lines from the injectors, took the three bolts out of the timing gear, and the couple of bolts that hold the cover on and lifted it straight up. Connect your IP to the other cover and set it straight down. That's what I did.
 
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Big Bart

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Welcome to oil burners!

I would also put your truck on TDC of the #1 cylinder at the power stroke. You can remove a glow plug and feel for pressure as you turn the crank to TDC.

Remove the IP as Jesus Freak mentions then loosen and lift the cover, not the gear. That leaves the gear timed.

Then set the new cover on with a seal or sealant without lifting the gear and tighten the cover. Put your IP back on. Put your rpm sensor in and hook up.

One other issue is now you have to time your IP again. So you need a timing meter. For info on that see this tech article

 

Jesus Freak

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The gear will kinda roll to one side or the other, as long as you don't lift the gear it'll stay on the correct tooth. And big Bart is correct, your timing won't be perfect but it will be close. After you read the thread about timing these engines, you're going to be all "hot and bothered" about timing it. I know I am, I gotta get one of those things!
 

rreegg

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Other posts had some great information. I believe to have had some tach. weirdness on my 88 idi due to faulty/corroded ground wires on the battery terminals. The tach would be working fine then drop to 0, then randomly come back. Just another thought
 

DaveBen

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If it were a grounding problem on the battery post you should see other faults like with a light or something.
 

Brian VT

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Isn't this his tach. sender? And he could test, or just replace, that to start with?
Sorry if I'm not following along correctly.
 

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Cubey

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Isn't this his tach. sender? And he could test, or just replace, that to start with?
Sorry if I'm not following along correctly.

No, that's going into the water jacket. The factory water gauge probe goes there, at least on both of my 6.9 engines.

Here's a fresh pic I just took of my RV to point this out.

I put my aftermarket gauge sending unit there because it was easier to reach than the dummy light port in the Econoline engine bay. You can see the factory wire hanging there next to it. On my F250, I put the water sending unit in the dummy light port, a bit further back towards the firewall.

That huge pipe plug there in the foreground is where the tach sensor would go.

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A web pic showing a tach sensor installed on a later housing with the angled filler and plastic threaded cap.

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