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Hey all, first time on here. Have an 88 4.0 automatic Comanche, as stated in the title the thing is  hesitating under load and spits and pops. Over the last few years I have replaced a ton of stuff on this thing. New intake/exhaust gasket, knock sensor, throttle position sensor, map and mat sensors, ecu, timing chain and gears, fuel pump, injectors, fuel pump relay, O2 sensor, complete exhaust system,  crank position sensor(on bell housing), and the idle speed sensor. There’s more but I think that’s all that would pertain to this issue. Recently replaced the timing chain and gears and it ran good for about 15-20 minutes. It overheated and shortly after ran like crap. As far as I can tell no blown head gasket. Has good compression in all cylinders 135-150. Any ideas? Do distributors go bad in these things often?

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Get some copper core plugs in it, what test have you done, have you done cruisers tips 1-5 and index the distributor. How are the vacuum lines, have you checked the line from the throttle body to the map?

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Did a smoke test and any lines leaking I replaced. The MAP vac line has been replaced. I unplugged all sensors and put them back on one  by one to see any change and nothing. I did try testing fuel pressure and came up with about 22 psi straight off the rail. My Haynes manual wants me to plug or unplug something on the throttle body when I test pressure but I have zero adjusting that I can see on the throttle body. Nothing to plug or unplug. Manual says it should be 14-15 psi, it’s kinda unclear to me how the manual guides you to test it for my throttle body. It looks stock to me. What is a proper way and what should fuel pressure be on this? 

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Fuel pressure should be 31 PSI with the vacuum line attached to the first pressure regulator. Fuel pressure should be 39 PSI with the vacuum line disconnected from the fuel pressure regulator.  

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When I was testing the fuel pressure I removed  the vac hose from the fpr And had no change. Replaced the fpr and still the same thing. The fuel pump I purchased through summit so I would think it’s a quality pump. The fuel filter has also been replaced. Also blew out the fuel lines and see no leaks. Would there be anything else keeping it from building pressure?

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11 minutes ago, ProblemPioneer said:

Problem Pioneer is back on the road!! Was a bad wire on on the hot side on the fuel sending unit. I attached a pic below. Made a new wire and it runs great. Thanks for all the input...

 

Nice work! It's alllive, it's alllllive.

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