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Danny Weimer 07-23-2014 04:44 PM

1990 302 back fire need help
I have a 1990 bronco full size with a 302 efi we have rebuilt the engine over a year ago. i am have a problem with back firing through the intake. This happens after being on the road for about 10 miles an running fine. the truck runs fine then loses power an when i give it gas the motor back fires. I have run Koer test an made all the repairs to that which was a egr switch an a broke line. I have have tested the fuel pressure when i turn the key on i get 23 psi i start the motor i get 35 i reve the motor it jumps to 40. the exhaust is only about 6 months old an the fuel was just topped off i am lost an ideas i live in the Dover Delaware an work in federalsburg Md if you would like to c or help me

Beechkid 07-23-2014 06:52 PM

Cough up through the carb typically indicates timing chain jumped a out of time.

Danny Weimer 07-23-2014 07:03 PM

Update i checked the timing an i was 20 degrees BTDC. i have reset it at 10 BTDC an going to c how it does on the way home. I tested in the shop parking lot seams a lot better but it wasnt warm. new chain u think it could b worn out in about 9000 miles to jump?

g_k50 07-23-2014 10:13 PM

Fuel pump pressure is low, replace fuel pump body.
There's a valve in the body that fails and fuel pressure drops due to the check valve being displaced.

Ford has the correct fuel pump body, fuel level sender is reused.
I had to do some soldering because the new fuel pump has updated connections at the point where the wiring connects to the fuel pump body.

Danny Weimer 07-23-2014 10:19 PM

Ok made it home went about 20 miles before it started acting up again changed mas air flow an that didn't fix it either. gK50 the fuel pump on this bronco is in the tank I agree I was thinking the pressure was a little low also I just now how much not fun they are to drop. But I am running out of ideas . The air in let is good spark is good an timing that just leaves fuel

Danny Weimer 07-23-2014 10:20 PM

Is there a fuel pump that is better than a other the one in there is about 6 years old 3 of them it may of been sitting

Kemicalburns 07-24-2014 11:11 AM

mass flow sensor??? that year bronco wouldn't be mass air so what sensor did you replace?

agree that fuel pressure is low, buy the complete fuel pump assembly from ford. best bang for your buck.

when you set the timing did you pull the spout connector?

Danny Weimer 07-24-2014 11:49 PM

The sensor on the. Passenger side right under the the whipper vise may be a map sensor either way it was a vacuum sensor an didn't fix it. So u also agree fuel pump weak

Danny Weimer 07-25-2014 05:40 PM

well did some more driving in the truck an as soon as the motor back fires an wont run again i put the trans in nuetral an the engine reves right up no problem an then back in gear an backfires more.

Kemicalburns 07-25-2014 05:53 PM

have you done a tune up yet? cap/rotor probably need replaced. also when you set the timing you must pull the spout connector, if you didn't do this the timing will never set correctly.

Danny Weimer 07-26-2014 09:50 AM

yes tune up had been done. an yes the spout was removed

Kemicalburns 07-28-2014 10:53 AM

perhaps the plug wires are not in the correct order on the distributor cap.

Danny Weimer 08-05-2014 11:44 PM

Ok up date a shop suggested to change the ignition module so I in stalled an rest set the timing an installed a fuel pressure gauge fuel psi stay around 35 An the engine still runs bad at any thing above a idle while driving to night I drive it about 3 miles before it started it stuff an I pulled over an in the dark I can c the cast iron hoarders glowing red. I check the cap an there was a lot of dentition so it cleaned the cap an rotor

Kemicalburns 08-06-2014 11:57 AM

replace the cap/rotor. if the headers are glowing you have a problem with either a clogged cat converter or your timing is really really off. was the distributor pulled at some point?

get the motor to TDC and pop the dizzy cap off and see where the rotor is pointing. it should be close to #1 on the dizzy cap. it may also be possible that if the dizzy had been pulled that it was put back in 180* off.

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