1990 F350 problem
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1990 F350 problem
Hello
New to the furum. So thanks in advance. Well I have a 1990 F350 with 7.5L that starts and then dies out. First thought it was was a tune up. I then replaced spark plugs with wire and distributor cap plus rotor. No luck. Next I took a friends advice and replaced TPS with same result. Stumped my buddy said he had a similar problem in his 89 which was the injectors, so I replaced those. I then had my buddy start it and before it could die I kept it running with some starting fluid. I grabbed a fuel pressure gauge and checked pressure @ 40psi while key was in the run position. But the pressure didnt hold. It seemed like after a second or to the fuel pump would shut off. This was the same for both tanks. I replaced both fuel pumps 5000 miles ago and think there still good. So today I change fuel pump relay, and EEC relay, fuel pressure regulator and still no where. Any sugfestion?
kamen1
New to the furum. So thanks in advance. Well I have a 1990 F350 with 7.5L that starts and then dies out. First thought it was was a tune up. I then replaced spark plugs with wire and distributor cap plus rotor. No luck. Next I took a friends advice and replaced TPS with same result. Stumped my buddy said he had a similar problem in his 89 which was the injectors, so I replaced those. I then had my buddy start it and before it could die I kept it running with some starting fluid. I grabbed a fuel pressure gauge and checked pressure @ 40psi while key was in the run position. But the pressure didnt hold. It seemed like after a second or to the fuel pump would shut off. This was the same for both tanks. I replaced both fuel pumps 5000 miles ago and think there still good. So today I change fuel pump relay, and EEC relay, fuel pressure regulator and still no where. Any sugfestion?
kamen1
Fleet Owner
Joined: Aug 2005
Posts: 23,666
Likes: 301
From: Easton,Ks
If they run for one second and quit then you know the fuel pumps, fuel pump relay, EEC relay are all OK.
Sounds like you have been getting some bad advice and it is costing you a lot of money. You should have come here first.
When the key is first turned on the computer will start a timer in the computer that runs for one second. This timer will ground the fuel pump relay.
Then the computer will wait for a PIP pulse from the distributor, when it sees a PIP pulse it will reset the fuel relay timer and the pumps will run for one more second. This PIP pulse will come faster than one second while the engine is cranking or running so the timer never times out as it keeps getting reset.
All of that said you either have a bad wire from the PIP sensor to the computer or a bad computer. Could also be the computer plug.
Sounds like you have been getting some bad advice and it is costing you a lot of money. You should have come here first.
When the key is first turned on the computer will start a timer in the computer that runs for one second. This timer will ground the fuel pump relay.
Then the computer will wait for a PIP pulse from the distributor, when it sees a PIP pulse it will reset the fuel relay timer and the pumps will run for one more second. This PIP pulse will come faster than one second while the engine is cranking or running so the timer never times out as it keeps getting reset.
All of that said you either have a bad wire from the PIP sensor to the computer or a bad computer. Could also be the computer plug.
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