hard starting and rough running
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Freshman User
Joined: Aug 2004
Posts: 26
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hard starting and rough running
89 ford diesal just the other day got real hard to start have to hold peddle down to keep running and idles real rough and i have changed fuel filter what else can i do
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
Check the fuel pressure from the lift pump.
Do pressure and flow test on the fuel at the Schrader valve on the filter(FSS- fuel shutoff switch disconnected). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.
If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation proceedure if it is the newer model pump with the almost straight arm.
Do pressure and flow test on the fuel at the Schrader valve on the filter(FSS- fuel shutoff switch disconnected). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.
If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation proceedure if it is the newer model pump with the almost straight arm.
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
I will say possibly.........if the L pump will not pump enough at cranking speed it may at hyway speed when it is running. The Lpump normally has a pressure of 4-6 psi, but the IP only needs 2 psi to operate with the right quantity.......fuzzy area for sure.
I guess that is why someone set those specs for a good Lpump test......at cranking speed. Gotta get it started first.........
I guess that is why someone set those specs for a good Lpump test......at cranking speed. Gotta get it started first.........
