94 4.9 f150 starting issues
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What do the plugs look like? Are you actually getting good spark at the plugs? Weak spark will carbon foul the plugs.Seen those ignition coils go bad too.
You need fuel, spark (at the correct time) , compression and air to run. It appears you have proper fuel pressure. Does it hold when the engine is shut off? If those two things check out, I would check and record compression of all six cylinders. If there is a weak link to the 4.9, I would have to say it is the nylon teeth of the timing gear shearing. That should show up on your compression tests.
You need fuel, spark (at the correct time) , compression and air to run. It appears you have proper fuel pressure. Does it hold when the engine is shut off? If those two things check out, I would check and record compression of all six cylinders. If there is a weak link to the 4.9, I would have to say it is the nylon teeth of the timing gear shearing. That should show up on your compression tests.
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what about the injectors. I have run sea foam through tanks to try to clean out the system. Would clogged or dirty injectors act this way.
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Forgot to mention to check manifold vacuum. Should be a steady 18-22 inches. You can also check for a clogged CAT while you have the gauge attached.
Last edited by raski; Sep 12, 2022 at 03:52 PM.
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mom so I had it running checking the pressures and it stalled. I switched take it retired then stalled. Pressure on gauge 43-45
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pressure holds. Or appears to. I will switch tanks. Rear tank seem to be issue. Both are acting same but rear is worse. Fuel pumps clogged. Have pressure by not volume.
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I would suggest since we are going around in circles, to start troubleshooting in a logical way and start ruling things out though proper testing..
Last edited by raski; Sep 12, 2022 at 04:10 PM.
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so change tank pumps?? I don’t see the other pump. Is it before or after the fuel filter.
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I don't think it is your injectors. They are pretty much bullet proof on a 4.9. I never seen or heard of any issues with them.See if pressure holds after shut down if your curious..
Forgot to mention to check manifold vacuum. Should be a steady 18-22 inches. You can also check for a clogged CAT while you have the gauge attached.
Forgot to mention to check manifold vacuum. Should be a steady 18-22 inches. You can also check for a clogged CAT while you have the gauge attached.
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Joined: Apr 2019
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Off the intake manifold. If you look off the side of the intake plenum on the top of the engine, there should be a junction point where many vacuum lines are connected to, facing the right fender.. I believe there should be a capped fitting that you can remove to connect your gauge.
With the fuel pressure you mentioned, I do not think you have a fuel issue. Even being on the low end of specs, it should be sufficient to run the engine.
Not that I am saying it is bad but the high pressure pump should be near the fuel filter.
With the fuel pressure you mentioned, I do not think you have a fuel issue. Even being on the low end of specs, it should be sufficient to run the engine.
Not that I am saying it is bad but the high pressure pump should be near the fuel filter.
Last edited by raski; Sep 13, 2022 at 01:04 AM.
Thread Starter
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Junior Member
Joined: Sep 2022
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Off the intake manifold. If you look off the side of the intake plenum on the top of the engine, there should be a junction point where many vacuum lines are connected to, facing the right fender.. I believe there should be a capped fitting that you can remove to connect your gauge.
With the fuel pressure you mentioned, I do not think you have a fuel issue. Even being on the low end of specs, it should be sufficient to run the engine.
Not that I am saying it is bad but the high pressure pump should be near the fuel filter.
With the fuel pressure you mentioned, I do not think you have a fuel issue. Even being on the low end of specs, it should be sufficient to run the engine.
Not that I am saying it is bad but the high pressure pump should be near the fuel filter.