Runs well but gets only 10 mpg and has a very strong exhaust smell?

SKYPILOT

MEMBER
1988 FORD F-150

Hello all.

I have a 1988 Ford E-150, Fuel Injected, V8 5.0L/302cid, with 118K miles. Vehicle runs well but gets only 10 mpg and has a very strong exhaust smell but it is not the "rotten egg" smell. Smells fuel "rich". Vacuum hoses appear to be good.

I'm thinking fuel pressure regulator? If FPR was bad, would that not allow fuel return and "force" (or dump) too much gas to injectors?

Miscellaneous info:

This vehicle has two gas tanks with a switch to change tanks but front tank will not supply fuel (probably bad pump) so I run off the rear tank.

Engine idle [u:c266ff9817]seems[/u:c266ff9817] a bit high but I can't be certain.

O2 sensor recently replaced.

Thermostat recently replaced

I have had -- but not recently -- an intermediate "check engine light".

I just purchased this vehicle (very cheap) and need to get this problem under control.

Thanks in advance.

3 Replies

BRUCE HUNT

MECHANIC
3,754 POSTS

Have tune-up and get the timing set. The code should still be in the computer so get a hold of the problem code.

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Monday, June 28th, 2021 AT 11:11 AM

CMMOORE

MEMBER
7 POSTS

I'd agree with the FP regulator. If it sticks shut pressure will dead head pump and cause fuel to pour through injectors. Also check for popped diapragm. Pull vacuum line at regulator and check for raw fuel. PCM might have a system rich code. Good luck!

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Monday, June 28th, 2021 AT 11:11 AM

SKYPILOT

MEMBER
2 POSTS

Thank both you guys. I took it into a trusted shop and they checked fuel pressure to rule out FP regulator -- it checked OK. The only problem was that the spark plugs were gapped incorrectly -- they were gapped as small as.30 whereas this vehicle called for.44. Replaced the plugs (gapped correctly) reset timing (which was off two degrees which was probably within limits) but that was really all they could find.

Also, I thought the vehicle was 302 cid when in fact it a 351 so maybe 10 mpg when fully loaded and pulling a trailer ain't all that bad. The exhaust fumes still seem too strong (rich) to me but that's a purely subjective determination. I live in a state where we don't (yet) have emissions control limitations so I guess I'm OK.

Genuinely appreciate the advice and hopefully someone else can benefit from this as well.

Mark

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Monday, June 28th, 2021 AT 11:11 AM