7.3 missing cold, Ok when hot, low power, boost - Ford Powerstroke Diesel Forum
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Old 11-27-2011, 11:54 PM
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7.3 missing cold, Ok when hot, low power, boost

Hello Ok here is info - 2001 *f550 7.3L 187,000miles * Outside temp. 75 degrees (hawaii) engine sitting 10 hrs. I start truck it *will idle rough, no power for 25mins, can't drive on any kind of incline, Flat road can drive a little, has a miss, but still very very little power, truck shakes, gets more power as it gets hotter after 25mins truck starts to pull like a different engine. If i plug engine warmer in 4 hrs it starts, little miss, low power for 5 mins then ok. Pass buzz test but injectors sound quiet to me.*Cylinder Contribution test when engine is just about warmed up, it said cylinder 4 and 8 injector circuit contribution balance fault. A few time said just cylinder 4. One day said 4 and 5. When engine is running for hours and hot cylinder contribution test said number 5 was bad. Tried cylinder contribution test when a little cold said numbers 3,4,5 bad. Also had low boost problem the Y flange behind turbo had big leak i change with aftermarket Y with new gaskets now boost gauge shows 15 max i cleared codes after new gaskets but autoenginuity shows code p1247 and 1248 boost pressure low and boost pressure not detected, but my gauge shows has boost. Cleared codes again and comes back.Y would that code show up?*
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Old 11-30-2011, 03:36 PM
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I had a 2001 f350 in my shop with what sounds like the same problem. It was hard to start and when it did, it ran real sluggish and skipped but no codes. I have seen this on a couple of trucks. It's probably going to be injectors. Pull the valve covers so you can see the injectors. On the top left corner of each injector there is an oil spill port. Start the truck and see how much oil is coming from each one. A bad injector can be identified by observing the flow of oil out of the spill ports. If no oil flow, the injector is not opening. If oil flows constantly, the injector is stuck open. A good injector will only have a very small amount of oil flow. With this method, I found 7 bad injectors. All injectors past the KOEO injector buzz test.
The no and low boost codes probably keep coming back because of the running badly. When a 7.3 runs bad like yours does, it doesn't create boost correctly. Even though your gauge shows you have 15psi, the ECM is not seeing the correct amount of boost at certain times. I would get the truck running correctly first and see if the codes come back.
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Old 12-13-2011, 02:31 AM
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Ok put 8 new injectors, new wiring harness, new valve cover gaskets, new MOTORCRAFT glow plugs. Cold start problem, rough idle when cold, and no power gone. Boost pressure at 18lbs now. Did it a little different than most people i pulled number 1 and 5 injectors out, tryed to get number 1 cylinder piston at lowest position, let 10 mins go by then pulled out all the rest. Then pulled out 8 glow plugs then sucked out oil with my wetvac threw injector hole :-) in number 1 and 5 then turned cranked shaft pulley about 5 complete turns by hand. Then put 8 injectors in then cranked engine by hand with glows plug out still 3 complete turns. Then put valve cover and gasket on WITHOUT harness on and WITHOUT glow plugs in and cranked engine for 5 seconds with ignition then pause for couple of mins then crank again 5 sec then pause the again couple of mins then cranked for 10
sec then pause then one more time for 10 sec. Then put glows back in and everything else. Once got truck started it took almost a hold day of driving to get it to stop smoking threw exhaust
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Old 12-18-2011, 12:29 AM
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I have a similar process to get the oil out of the cylinders when doing an injector change. The way you did it sounds fine to me. It is normal for the truck to smoke after an injector change. Even though you went through your process to get the oil out, there is still some oil left that just has to burn out. Nothing to worry about. as far as your cold start problem, shaking when cold and no power loss, sounds like glow plug related to me. Glow plugs and harness are new, I would probably start with the glow plug controller. Just do a search on here on how to test it. Also might want to check the wiring from the glow plug controller to the valve cover harness.
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Old 12-30-2011, 08:33 PM
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so after you changed your injectors did it still throw the code low boost, and what type of guage are you using to monitor boost and where is it connected?
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