This may get lenghty. I have a bxs acert i put a cam in . Driver picked it up , returned with a stumble ? at part throttle. I have since determined it is over fueling now this is where it gets interesting. Originaly fuel pressure was about 140 psi. I removed a shim from the pump put in a different regulator and dropped it to 110 psi. Still have over fuel condition . Changed cam timing 1 tooth both directions it will set a code. I checked valve lash with it at operating temp ran it and watched nothing is amiss iva adjusted all the way out. I have taken it to several other good techs consensus was ECM took it to cat, it had many injector fauls so we replaced it. No change in fueling problem. Took truck to cat cut out all cylinders with it overfueling none made a difference. Cat tech suggested fuel pressure still to high . Back home replaced fuel lines on engine , had run the truck with short hoses off a 5 gal bucket with no change earlier. I have since replaced the fuel pump, fuel regulator and bypass valves, just got done replacing the injector o rings to no avail. Fuel pressure now at 90 psi.
This is the condition it acts up in . Steady speed with a slight increase in throttle it will shudder blow out a wad of smoke and some times clear up or get worse. If you floor it or let completely off it clears up. I can run the engine parked to full speed no load 2100rpm gph is 6.2 if I back off to 1600 -1700 then ease back into it it will smoke and run rough gph goes up to 12-14 I can slowly increase or decrease engine speed while its over fueling, again if it's floored or let off quickly it will clear up. while at high rpm it will build 20+ psi boost. No faults in ecm. The truck has good power when it is normal I have driven it as much as 40 miles before it will act up. As of right now it will do it at any temp at least 50 or up. HELP When I say smoke it is blue due to fact it cant burn it, smoke like a old cummins on a cold day at start up. pyro stays low 500 or less, all sensor readings are normal, nothing to indicate a sensor failure.
Help needed from the cat Gurus
Discussion in 'Trucks [ Eighteen Wheelers ]' started by 1johnb, Nov 15, 2012.
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Did you use the original cam gear or changed it? The cam you installed is a factory replacement.
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is the camshaft the correct part number?
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Where are you checking the pressure? If its before the engine filter, it's stopped up. That's awful high. Gauge accurate?
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Used the old one looked good. Also forgot it will do this with cruise on. It feels like a tps with an open, except for the smoke. I tried 3 different people from Cat to find the criteria the ECM uses to calculate gph no one knows.
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10R2111 cam had a 207 7508. 90psi is spec 93 max cat tech said a lot run 100. More than 1 gauge and yes accurate both read the same.
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Is it the right cam?
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Filters replaced twice. Another thing is if I remove the boost sensor while this occurs it will clear up and yes it is new.
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Did you adjust injector hight while engine is cold?
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Yes twice. I was questioning the cam but it runs to good when it is right. Also if it was a problem with the grind being out of time it would have been noticeable while setting the overhead. I don't think it's related to the cam. Supposedly it wasn't acting up before the cam. But I think that may not be true.
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