No Power, Hard start, bad mileage - Ford Powerstroke Diesel Forum
7.3L IDI (Non-Powerstroke) Diesels Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

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Old 03-02-2010, 03:22 AM
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No Power, Hard start, bad mileage

I have a 94 F250 4X4 7.3L IDI turbo that is very hard to start, no power and awful fuel mileage. Once it starts, the idle seems to be fine though. I have read all the posts I can find about this issue and it looks like injectors and IP timing should take care of it. I have a couple of questions though. I have the injectors installed but before I get it fully assembled, is there anything I should check or watch for that I may have missed? The installation kit (return lines) came with new fittings but two of the originals were a tee that connected the left and right sides together and the new fittings had no tee. Is that crossover necessary? My biggest question is on the IP timing, previous posts indicate that in time the pump retards and simply has to be adjusted. I haven't messed with it yet but I found the timing marks and they are dead nuts on. How far and what direction should I turn it? and what is actually causing it to retard? I found three bolts on the thing but how do you even get a wrench on them?
I still need to get an EGT and boost guage before I mess with turning up the fuel or adjusting the waste gate.
Thanks, and sorry for such a long question.
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Old 03-02-2010, 05:59 PM
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I think you hit it on the nail with timing, as bad timing (retarted) sounds like your symptoms.

The cross over cap is needed, as the fuel will go into the return line on the drivers side, so they are needed.

Some people bend a wrench to get down and get the three bolts. I adjusted my timing when I had my engine out for head studs. I believe you rotate the IP once loosened, towards the passenger side. A dimes width is a couple degree's of timing, so dont go crazy. I would try a dimes width first.

Or pm me, and I will try to set you up with a guy that has a timing meter up in Michigan. Most of us IDI guys will stick together and help each other out. If you are close I'm sure they would help you.
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Old 03-03-2010, 05:17 AM
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Thanks for the info. I won't be able to work on it again until the weekend but I am really hoping this brings her back to top form.
Can you adjust the timing with the engine running like on a gasser or does it have to be off when you turn the pump?
I assume that I will have to bleed the lines at the injectors before I start it the first time, should I do them one at a time or can I do them all at once?
What causes the timing to be off, is the fact that I have to adjust the timing an indication that the pump is wearing out? Is there a tell-tale that indicates when a pump should be replaced? I think I have just over 200k on the truck now and as much as I can tell, nothing has ever been adjusted, the injectors were original and the pump looks like it has never been touched. A couple of years ago I put a new glow plug relay and some new glow plugs but that is it until now.
Thanks again. I love this forum.
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Old 03-03-2010, 02:26 PM
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As you said, as the injetion pump ages the timing retards. It does it so slow most people dont notice.

Truck has to be off to time it I believe, or at least that is what I would do. Just make sure to not rotate it that much, a little bit goes a long way.

There are no real tell-tale signs, unless something goes wrong like it wont start when the engine is warm. That is usually a sign. I've heard of some pumps lasting 300K+ miles, and others lasting 50K miles, it just depends.
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Old 03-14-2010, 04:11 AM
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Thanks for all your help.
I finally got it back together and running but I wont know how effictive it was until I can run a tank through it and check the mileage. It definately seems to have more power but I haven't tried pulling anything yet. I must have missed something though because it sat all last week and when I got home on Friday, it started really hard again. Still acting like air in the lines but after new injectors and return kit, I have no idea where to look now. Once it starts, it idles rough for a few seconds then smoothes right out and I noticed very little smoke which was white. I will try to start it later today and see what it does after only a couple of days but I expect pretty much the same.

Something I can't seem to get my head around though is the return lines are just retunring excess fuel to the tank, they aren't part of the pressure loop so air getting in there would seem normal (once the fuel has returned to the tank). The fuel between the injectors and pump should still be there. A while back I put a vacuum guage on the mechanical pump and it checked fine for whatever that is worth.

This system is relatively simple and it is driving me nuts that I can't figure out what is happening here. It definately isn't helping with the wife's opinion of diesels.
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Old 03-14-2010, 06:05 AM
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Might want to make sure filters are clean and the tank vent is clear. Sounds like fuel starvation to me.
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Old 03-15-2010, 03:13 AM
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Both tanks as well as the lines are new. The filter isn't new but it isn't very old either. Also, it seems to be more like many other posts I've read where it is hard to start but once started, it will start right back up on the first turn. It is only hard to start after it sits like overnight.

I thought I had read somewhere about a check valve or two that is supposed to keep the fuel from draining back to the tank on the pressure side but my manual says nothing about them and I have no idea where to start looking. Does anybody know where it might be?
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Old 03-18-2010, 03:33 AM
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I hope I'm not the only one that has had this problem?
I also thought of something else, what kind of issues can you get from the fuel tank selector valve? Everything seems fine on the front tank but when I switch to the rear tank you can feel the power drop right off. Consequently, I don't use the rear tank.
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Old 05-16-2013, 10:29 AM
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m-hickey95 what did you find out about your problems
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Old 07-02-2013, 05:06 PM
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1994 IDI hard to start rough idle

Hello new here today, forums are great help so idecided to add my fix today my 1994 IDI was running fine, then started to run rough and hard to start,crack injectors, all good,checked fuel filter good. hopeing it wont be injector pump, I hit the fuel selector switch to rear and now runs fine, easy start and smooth running, My front fuel pickup screen or pump is clogged or bad.
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