My Ongoing Repair Thread for my 93 - Lots of Pics, Vids, and Details. Please HELP!

[daustin]

I would be leary of tieing it to an ingition source, if the factory lift pump stuf isn't working i'd really try to get it working. It works good when it's in proper condition and had some safety measures built in as well. A mod that's been popular and works well is to utilize the OPS to drive a relay, thus preventing the infamous OPS contact "burn-out" that plagues the OPS units.
Don

 

[buddy]

many people have modified the LP circuit to run before cranking specifically for hard starts, and they did it in 96+ for a reason. If there is a switch on the IGN source, a flip switch or even momentary, or a temp switch it will resume OPS operation when it gets shut off.

 

[daustin]

Yup, but his is a '93 and from the factory it should do that already. That's why i was saying that i'd fix what was broken by the PO instead of adding to the wiring mess.
Don

 

[buddy]

Yup, but his is a '93 and from the factory it should do that already. That's why i was saying that i'd fix what was broken by the PO instead of adding to the wiring mess.
Don

I thought you said the exact opposite, only comes on when OPS is greater than 6psi, which isnt happening until you crank. You put the big AND in there, when maybe you meant EITHER, or OR. I thought you were stressing the point AND meaning both had to be true, since you were talking logic speak. But when I reread it I can understand it now.

so what you mean is that its supposed to work when just the GP relay is going? Do you have a wire diagram that brings the purple/white wire of the LP relay back to the GP relay?

Or maybe the A wire on the relay goes to the GP relay, and they took it off on 94 and put it to the diagnostic port pin G. But purple/white still go to crank.

 

[tracy]

Hi guys,
According to my GM manual, it will energize the lift pump relay when the "WTS" (Wait to Start) light is on (that's when it cycles the glow plugs), "START" is true (starter is turning over) AND when the OPS is "true" (Oil Pressure > 6lbs). These early models with the mechanical IP are a little different than the '94 and up. I had read up on it a lot on several other sites, and mine wasn't working like it was stated for the ODB-I type machines. I then got out my GM manuals, and read every scrap of info i could find on it. Found out my '93 was working just like the book said it was supposed to. The mechanical IP powers the lift pump when the WTS is on, START is "true" AND when the OPS is true. My estimate of 3-5 seconds was a little off, it's tied directly to the "WTS/Glow Plug" operation, thus it varies somewhat. I'm a control systems engineer so i'm always interested in how things work thus i research things in detail, one of my faults according to my wife. lol My '93 has about 205,000 miles on it, original engine/heads..etc (Tranny was rebuilt at 202,000) and runs like a top. Very very happy with it. I don't let any shop touch any of my cars except for front end alignments, tire installs or things like that which i don't have the specific tools to do. I think they are all screwing me every time. HAHAHA My hobby is restoring 50's-70's musclecars i built a 1200 sq ft shop in '01 to mess with my stuff in. All my friends & neighbors come over and we mess with my cars and theirs when needed. Hope that helps explain things with the lift pump, ops, WTS..etc for the '93's.
Don

Thanks for that info Don, the lift pump on my 93 doesn't operate during WTS cycle, You don't off hand remember were the power to operate the lift pump comes from during WTS cycle. Maybe from the glowplug contoler?

 

[Turbine Doc]

Symantics really, the 96+ turn on when the IGN is in the ON position, triggered by direct feed to the PCM from the IGN. A relay is a switch, a switch can be a relay, not much difference in definition, and the OPS meets definition of a relay better anyway.

Not semantics in automotive world, go to part store and ask for a relay see what you get if you want a OPS, or ask for a OPS if you need a relay see which one you get.

And as far as the logic how/went it powers up in a OBD-II, when I get time I'll update the OPS/Lift thread, required some real world under-hood testing by plugging and unplugging the (2) different power paths at same time to fully understand it, schematics in the GM manual can lead you to some incorrect assumptions.

Don if you would could you please add the lucid explanation of the 93's operation :thumbsup: to the OPS thread http://dieseltowingresource.com/showthread.php?t=6872 as it will be part of reference material one day.

 

[buddy]

Not semantics in automotive world, go to part store and ask for a relay see what you get if you want a OPS, or ask for a OPS if you need a relay see which one you get.

Asking for a part name and what function it serves is a little different, the Oil Pressure Switch is a relay, which are switches.

 

[daustin]

I thought you said the exact opposite, only comes on when OPS is greater than 6psi, which isnt happening until you crank. You put the big AND in there, when maybe you meant EITHER, or OR. I thought you were stressing the point AND meaning both had to be true, since you were talking logic speak. But when I reread it I can understand it now.

so what you mean is that its supposed to work when just the GP relay is going? Do you have a wire diagram that brings the purple/white wire of the LP relay back to the GP relay?

Or maybe the A wire on the relay goes to the GP relay, and they took it off on 94 and put it to the diagnostic port pin G. But purple/white still go to crank.

Buddy,
If you notice the first sentence in my paragraph, it says it's powered on when the WTS (Wait to Start, or glow plugs on indication") is on. If you turn the key on but don't actually start the truck the pump will have power until the WTS goes out, not indefinatly if the engine isn't running. I'll scan the pages from my FSM for the '93 models, schematics and their description (which i may have indeed buggered up lol). The mechanical IP's are a different animal from the OBD-I and OBD-II trucks, last of the dino's with mechanical injection pumps. Since mine was unaltered when i got it (well except for the exhaust) i'm 99% sure it operates right for a '92-93 when matched against the FSM's description/schematics. When i first got it a few years ago, the cold IP advance and glow plugs didn't work so i researched it and found a bad sensor, bad OPS and broken glow plug wires where they had contacted the exhaust. (not uncommon on these trucks). After replacing the sensors, and a couple burnt wires it started working like the book said it should. I'm not trying to argue, just explain what the mechanical IP trucks do as it's different from any of the '94 up trucks.
Thanks for hearing my "ramble".
PS: Doc, i'll get that stuff scanned and get it posted in the reference area - might need your help with that. Thanks

Don

 

[Classified]

Ok, did some more testing with the LP.

The factory purple/white LP turn on wire does power the LP when cranking. But instead of hooking up the wire back to normal, I chose to have the LP power up when the GPs are powered up. But before I did that, I disconnected the the power from the IGN to power up the relay, started the engine and then checked to see if the OPS was powering up the LP which it was not! So I replaced the OPS (what a pain) and its back to working like normal.

Today I started up the engine, dead cold and it started instantly and it didnt really smoke at all!


Now I have some more questions, sorta related too.

I let the truck run at one point for about 20 minutes letting it warm up. I turned the truck off and then started it about 20 minutes later. Its was very hard to start and smoked like crazy for about 4 minutes but in total for about 10 minutes. It was like a totally different truck from earlier. The LP was working and everything. Also, the truck was doing that puffing thing out the exhaust but not as often. I went to grab my camera to video it and it had stopped (1 minute) and the exhaust was back to clear.
Does this sound like a timing issue? I did take a video anyway, fast foward to 40 seconds, there was a random puff of smoke. I then tried to provoke the puffing by revving the engine.

http://www.youtube.com/watch?v=HlqfhtltZsk


I know you all said injectors before, you think that what it is still? or the timing?

 

[ShawnR]

I played with the pump timing on my 93 today and it acted similiar when it was retarded. It would idle fine, but when I gave it any fuel, the white smike would puff out. I advanced it back (toward drivers side) until no more white smoke. It is still more retarded that it was before I started tinkering.

It does have less power, but it is SOOO much quieter & smoother. No more CLACKETY, CLACKETY, CLACKETY. Now it is more like a duramax's rattle, rattle, rattle.

It still starts like crap, but that it another issue.

So, my theory is that pump timing is retarded and the cold start advance put it about to the right place. That is why it started good and ran fine when cold. Of course, I could very possible be completely wrong. It wouldn't be the first time.

 

[buddy]

You could try turning your fuel output down or up, easy enough on the mechanical pump.

And it makes sense what Shawn says. Id try advancing before spending money on injectors.

 

[Classified]

You could try turning your fuel output down or up, easy enough on the mechanical pump.

And it makes sense what Shawn says. Id try advancing before spending money on injectors.

The fuel screw is under the intake though right? Its on the IP but I have to take off the metal intake that goes to the turbo right?

I will try to advance the timing then. Can I do this with the engine running? LOL Im sure that sounds stupid but just making sure that the engine should be off.

 

[Classified]

I played with the pump timing on my 93 today and it acted similiar when it was retarded. It would idle fine, but when I gave it any fuel, the white smike would puff out. I advanced it back (toward drivers side) until no more white smoke. It is still more retarded that it was before I started tinkering.

It does have less power, but it is SOOO much quieter & smoother. No more CLACKETY, CLACKETY, CLACKETY. Now it is more like a duramax's rattle, rattle, rattle.

It still starts like crap, but that it another issue.

So, my theory is that pump timing is retarded and the cold start advance put it about to the right place. That is why it started good and ran fine when cold. Of course, I could very possible be completely wrong. It wouldn't be the first time.

Well mine starts awesome and it was the OPS not working. Check to make sure your LP is running, I wired mine to turn on with the GPs, that way it primes the engine and then starts right up. It runs MUCH MUCH better now.

 

[buddy]

You do NOT want to adjust timing while running. Like Shawn said move mark towards drivers side.

Is it still running after turning IGN off? Have you monitored the voltage at the solenoid to see that it goes away when you turn IGN off.

 

[Classified]

You do NOT want to adjust timing while running. Like Shawn said move mark towards drivers side.

Is it still running after turning IGN off? Have you monitored the voltage at the solenoid to see that it goes away when you turn IGN off.

Ok just makin' sure,LOL.

It still runs for a few secs after the IGN is off and I did not monitor the voltage as I shut the engine off but I Did make sure it did not have voltage while off and voltage while on and it did.

I unplugged the pink wire from the solenoid while the engine was running and it did shut the engine down immediately. I think the key cylinder is funky because sometimes the wipers wont work until you joggle the key a little bit.

 

[daustin]

That sounds like the actual switch, not the key cylinder itself. The switch is on the column more or less where it goes by the lower dash, actuated by a rod from the lock cylinder. That's pretty easy to change, unlike the cylinder itself where you have to take the steering wheel..etc off. Also turning up the IP, what i did was pop off the upper intake and take the littke triangle off the drivers side of the IP. Then i used a small mirror, barred the engine over until i could see the allen socket. Turn 1/4 (more or less) to the right. Close up and your done.
Don

 

[buddy]

I would monitor that shut off voltage as someone turns off the truck. That could absolve the IP solenoid itself of being bad and lead you elsewhere. Just poke a test light or meter lead onto the wire while its plugged in and running then shut the truck off to see if voltage goes away immediately with the ignition off.

 

[daustin]

I thought he said he unplugged that connector at the IP and it died immediatly, that's why i suggested the switch on the column, but i could have read it wrong. lol
Don

 

[buddy]

I thought he said he unplugged that connector at the IP and it died immediatly, that's why i suggested the switch on the column, but i could have read it wrong. lol
Don

Youre right, unplugging it works, so that would suggest the solenoid is fine, so it must be getting voltage elsewhere, perhaps the IGN switch. Why not confirm there is still voltage there before monkeying with it.

 

[Classified]

Ok, the delay to the truck turning off is NOT the solenoid on the IP. Its a delay somewhere else, I probably wont mess with it, well see how deep I get into the dash since its getting close to the next thing on the list.

I was going to advance the timing some today but ran into an issue, how the heck do you get to the bolts? Its the 3 bolts right? I have a picture to make sure I have the right bolts, but I have no idea how to loosen them. I also didnt mess with the fuel screw yet, I got sidetracked dealing with the trans issues. But Ill make that a different thread.