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Thread: 1994 F150 5.0L Won't Start...

  1. #1
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    1994 F150 5.0L Won't Start...

    Hey folks...friend of mine has a 94 F150 with 5.0L Fuel injected engine that won't start. He recently installed a rebuilt long block and when the mechanic started it there was popping in the exhaust. He fiddled with the distributor and got the popping to go away but the truck ran with a choppy idle as if it were missing out. The mechanic went on to other projects. My friend backed the truck up about 30 feet and said the engine was running very quietly but began to idle rougher and rougher, then died. Now it will not start at all. We installed a new distributor to no avail, then checked the codes. It passed EVERY code test...no malfunctions indicated. The coil checks out fine and there is fire at the sparkplugs. There IS a strong gasoline odor as the engine turns over and tries to fire...with the throttle body butterflies held wide open. Use of starter fluid once resulted in a HUGE backfire. My question is about the fuel pressure regulator. If you suck on the vacuum line attatched to it you cannot hear it move in any way and can faintly taste the gasoline. If this regulator is stuck open, will it cause the injectors to flood the cylinders due to abnormally high fuel pressures? Any other suggestions??? Thanx for any help!!

  2. #2
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    Sounds like the new dist. is installed incorrectly, and the thing can't compensate enough to make it fire. Just because there is spark, does not mean that the spark is firing at the correct time.
    The fact that the thing backfires when you spray a very combustible mixture indicates that you are getting fire at the wrong time.
    Fuel related problems (like too much) would simply run rich and smoke, but would not backfire.

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    I agree, but at #1 cyl TDC the rotor is pointing directly at the #1 terminal on the cap. I've located TDC two different ways...1. Remove plug and hold finger over hole until pressure builds, then continue turning over by hand using a screwdriver inserted to top of piston as guage. 2. Remove plug and hold finger over hole until pressure builds, then turn engine by hand until 0 is indicated by pointer on harmonic balancer scale. Is this the wrong technique? (#2 was used when installing the distributor) UNRELATED ADENDUM: When I removed the old distributor the oil pump driveshaft came up with the distributor. When I went to re-insert the new distributor, the shaft was leaning against one side of the hole in the block. I lifted the shaft up and inserted it into the bottom of the distributor to be able to fully install the distributor. The shaft would NOT come completely out of the engine. Is it possible the shaft MAY not be engaged with the oil pump????

  4. #4
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    the shaft is likely engaged. First thing first with all fuel injected motors- verify proper fuel pressure, and set the timing with a gun to the proper spec. then go from there. check for vacuum leaks and stuff.
    Joe
    89 K2500 Chevy, Wee-Oh-five 294K miles
    1962 Scout 80 parts I guess
    1966 Scout 800 resto job
    2005 Chevy 2500HD Short cab long box DURAMAX
    1996 P30, 6.5 NA Mac Mobile
    whole lot of buicks

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    Fuel pressure brings me back to my original suspicions concerning the fuel pressure regulator...can it fail and cause an increase in pressure that will flood the cylinders preventing starting the engine?

  6. #6
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    the regulator is wide open until vacuum is applied to it, so if it failed it would really only create a rich, but runnable condition. the only way it would flood out is if an injector stuck open. does the truck have dual tanks? Those valve between the tanks go bad frequently due to rust and corrosion, often times causing low pressure, no pressure, power to either pump, and erratic fuel gauge readings.

    I just read that you can taste gas when sucking the hose () sometimes the regulator can go bad and bleed fuel pressure into the intake. run the fuel pump with the vacuum line off, and if gas shoots out the regultor hose, then its shot, but likly wouldn't cause a no run. It would act like an old school cold start valve.

    Really, get a fuel pressure guage, and a timing gun and verify they are within spec. also, check to make sure the distributor isn't 180 out. that often times causes a backfire out the intake. of course your plugs could be fouled out at this point too.
    Joe
    89 K2500 Chevy, Wee-Oh-five 294K miles
    1962 Scout 80 parts I guess
    1966 Scout 800 resto job
    2005 Chevy 2500HD Short cab long box DURAMAX
    1996 P30, 6.5 NA Mac Mobile
    whole lot of buicks

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    Update #1...Went back to basics and checked timing and engine electrical. Found three spark plug wires that were not pushed completely onto the plug and one that the boot had pulled far enough off that the connector was not visible. Can't get good help these days....that's what I get for ASSuming things were done correctly. Anyways, got it started and now it runs OK at high rpms, but idles horrendously(actully won't idle, and runs rough just off idle). Bit the bullet and bought a fuel pressure guage so I'll check out the injectors next.

  8. #8
    Senior Member tjzz4's Avatar
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    Is it rich? (lotsa black smoke)

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    Not really running rich...NEW WRINKLE: Local mechanic guy informed us that the parts store could have substituted an older 302 engine for the necessary 302HO that is called for with the 94 fuel injection. He says this means a different camshaft that is INCOMPATIBLE with the 94 truck computer and the only way to get it to run properly is to switch out the camshaft!!! He says rerouting the plug wires will help, but will create problems with injectors firing improperly. CAN THIS BE TRUE???? If so...can the computer be reprogrammed, or the injectors rewired to reflect the different firing order???

  10. #10
    Junior Member 88f-150man's Avatar
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    If it is infact a 302 h.o. and it has a h.o. cam in it all this means is that it has a 351W firing order. What firing order are you running? Did the truck come stock with the h.o. or is the replacement just an h.o. If it's not a stock h.o. then it might help to change the cam and firing order.

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