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Hard start, rough running 94 7.3

5K views 17 replies 4 participants last post by  Mustangranch22 
#1 ·
Ok I just picked up a 94 7.3l. I have a few different issues/questions. When I got the truck the hpop leaked like crazy. Pulled it off and happened to pick up a 99 hpop. Did the swap with the drain back mod that I found on here. Truck still starts hard!!! All glow plugs are good. Harness under the valve covers are good. Once you get the truck started it idles horrible. (oh I changed the oil to 5w40 synthetic rotella) I put a temp gun on the manifolds. 3 cylinders are dead cold while it idles. Once it warms up its like a light switch gets flipped and the truck rins better than my 97 did I'm stuck on where to start with my diag. My scanner won't talk to the PCM, so I can't run a buzz test or watch cranking oil psi etc. Trying to decide if I have an oil system issue or some injectors bad. (sorry shoulda mentioned truck has 250k and I think they didn't do good pm on it). So do I send te PCM in and have it flashed to be obII compatible? Which if I do that who is good to send it to. Or try to find a 97 PCM? I know that'll help to diag obviously. Just curious too if there's any known oil issues in the oil system in the heads or anything. Thanks in advance since this has prob been asked 100 times.
 
#2 ·
Ok I picked up a pcm out of a 96 cheap so I'm going to plug it in and see if I can run the buzz test with it. I found another post on here somewhere that had the same numbers as mine and said that it should work to do so. I think #1,4,8 injectors are bad so heres hoping I can confirm with the buzz test.
 
#8 ·
Well no. Instead I read somewhere I could just put it into my scanner as a 96 and see if they'd communicate. So I tried that just now. Showed inj pressure hen the truck was cranking 175 rpm's to be 3000. Ran a buzz test it showed system pass. I plugged the glow plug relay in and the truck fires up but misses just as bad as ever. Watched inj psi at idle was 800 ish dyer to came back down from 3000. Truck doesn't appear to drinking oil so not sure if I should re prong the injectors that are cold? I checked them with a temp gun is how I figured which ones I assume are bad. I wanna fix it right not just throw parts at it while I learn.
 
#10 ·
If they are both for the same transmission, you could use it, but there would probably be no real advantage. You would need to clear any codes once its installed and then see what pops back up.
 
#11 ·
It's not throwing any codes. It just wouldn't communicate with my scanner till I entered the vin in my scanner as a 96. So if there's no advantage then I won't waste the time ya know. I didn't know I the 96's had any other advantages is all. Thank you. I'll post hopefully what I figure out with the misfire this weekend. I picked up a set of injectors. (used) which I know equals crap shoot to fix the problem but hey have a lot fewer miles on them than my current ones.
 
#12 ·
Who's the best to send a turbo to, to have rebuilt? I saw apost somewhere about a place in Utah I think? I have a turbo for my truck with 60k on it so I am going to put a beans 1.0 on it with a downpipe then thought about sending the one on my truck currently in to have it rebuilt since it seems to blow oil everywhere and have it rebuilt to sell as a rebuilt? or is that just money/time waisted?
 
#13 ·
Ok I have done a fair amount of work to the truck and I am still having one small issue. Here's a quick rundown of the repairs I made. I replaced 4 injectors on the 4 that I deemed bad before. They would fire when cold? and I replaced all injector O rings on all 8 injectors. I replaced the turbo and installed a beans 1.0 exhaust housing. 2 Injectors had O rings that were taost and dumping oil causing the hars cold start. Now the truck starts pretty dang good but 1 injector still doesnt fire until operating temp? and passes a buzz test. any thoughts?
 
#14 ·
Injector buzz test will almost always say "pass". You need to apply common sense and listen to each buzz for one (or more) that sounds weird or is non-existent.

I'd check harnesses next.
 
#15 ·
Well that's the first thing most tell you to do is the buzz test. I did apply comon sence and listened. I am not trying to figure out which injector it is , ( I can figure that out easy enough) I am trying to figure out why? Could the inside have gotten scored by lack of oil or? I checked harnesses and vavle cover gaskets. I figured if it was electrical it would get worde with heat not start working like somone turned on a light switch.
 
#17 ·
Well I m experiencing the miss fire cold still and a new problem showed up. I hauled my car to town the other night, approx 30 miles and stopped at afriends house. after the truck sat for approx 2 hours I started it to leave. Truck started fine but then sounded lik it was running out of fuel. Stopped and put $20 in it cause it was low and the check engine light came on. Very low on power this whole time. I limped it home thinking it ran so low I got air in the fuels system or something. Next day the truck ran fine. Intermittenly now the check engine light comes on and truck goes in to Limp mode. Pulled codes and I get a P1211 code. While the code is showing and truck running I have 2400 psi +/- wot ijections psi at around 42% duty cycle. at idle it runs approx 550-600 psi at about 9% duty cycle and .9v.... I've done some reading and most say the hpop is dying just looking for ideas of where to even start on this thing. It's gettting frustrating
 
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