EFI - losing revs when revving + under load

Discuss modifications on your 1979 to late 1998 SFA 4x4 Hilux here.
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Jaco Versfeld
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Tue Sep 25, 2012 12:13 pm

Hi There,

I recently "serviced" Mufasa, did an oil change, new spark plugs and replaced the low pressure fuel filter in front of the High pressure pump. (At what intervals should I replace the high pressure filter?)

Any case, recently Mufasa is struggling at higher revs, around 3700 - 4000, the car will lose momentum and then go and lose momentum. The rev needle will also fall about 100 or 200 revs. This is aggravated if I am going uphill, or have a wind from the front.

Lately Mufasa is idling very low, at around 400 - 500 RPM, even when warm.

I also hear the fuel pump cavitating some time.

Are there any tests that I could do to fault find the problem? (I would love to get Mufasa right for Saturday's day trip at Berakah...) I suspect that the fuel system might get in some air due to me fiddling with the fuel filter. In the past, if the MAP sensor pipe came lose, the engine didn't rev correctly.

Any other suggestions?

Thanks,
Jaco
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CasKru
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Tue Sep 25, 2012 12:20 pm

Sounds like fuel starvation. Did you fit the correct size fuel filter and did you fit it the correct way.
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Jaco Versfeld
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Tue Sep 25, 2012 12:27 pm

CasKru wrote:Sounds like fuel starvation. Did you fit the correct size fuel filter and did you fit it the correct way.
Fuel filter is definitely fitted correct way - I double checked.

The the diameter of the fuel filter's pipes are 8 mm, is there anything else I should take into consideration?

Thanks,
Jaco
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CasKru
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Tue Sep 25, 2012 12:34 pm

Jaco Versfeld wrote:
CasKru wrote:Sounds like fuel starvation. Did you fit the correct size fuel filter and did you fit it the correct way.
Fuel filter is definitely fitted correct way - I double checked.

The the diameter of the fuel filter's pipes are 8 mm, is there anything else I should take into consideration?

Thanks,
Jaco
Did the fuel pipe not maybe kink when you worked on it? It sounds like the HP pump is batteling to get enough feed to maintain the fuel pressure needed. At low engine RPM you will maybe not notice it but the higher the RPM the more pronounced it will become.
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Jaco Versfeld
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Location: Fairland
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Tue Sep 25, 2012 12:38 pm

CasKru wrote:
Jaco Versfeld wrote:
CasKru wrote:Sounds like fuel starvation. Did you fit the correct size fuel filter and did you fit it the correct way.
Fuel filter is definitely fitted correct way - I double checked.

The the diameter of the fuel filter's pipes are 8 mm, is there anything else I should take into consideration?

Thanks,
Jaco
Did the fuel pipe not maybe kink when you worked on it? It sounds like the HP pump is batteling to get enough feed to maintain the fuel pressure needed. At low engine RPM you will maybe not notice it but the higher the RPM the more pronounced it will become.

Thanks Cassie, I will check.

I do smell fuel when I have driven the vehicle, therefore my suspicion that I didn't fasten one of the clamps. But I will check if I didn't bend the fuel pipe while replacing the fuel filter.

What is the replacement interval on the HP filter?

Thanks,
Jaco
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CasKru
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Tue Sep 25, 2012 12:40 pm

Jaco Versfeld wrote:
Thanks Cassie, I will check.

I do smell fuel when I have driven the vehicle, therefore my suspicion that I didn't fasten one of the clamps. But I will check if I didn't bend the fuel pipe while replacing the fuel filter.

What is the replacement interval on the HP filter?

Thanks,
Jaco
aaaah... sounds like you are sucking in air on the inlet side :thumbup:

Not sure about the canister type fuel filters but I replace mine every 30 000km
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Mr_B
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Tue Sep 25, 2012 1:03 pm

Check that the vacuum pipe hasn't dislodged or got bent/blocked on the plenum chamber or behind dicktator ECU itself. Happened on Bolt, I fitted a T piece to stop the pipe snagging and getting blocked. It's critical that there are no leaks/blockages on the vac circuit.
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Tue Sep 25, 2012 5:28 pm

Jaco Versfeld wrote:
CasKru wrote:Sounds like fuel starvation. Did you fit the correct size fuel filter and did you fit it the correct way.
Fuel filter is definitely fitted correct way - I double checked.

The the diameter of the fuel filter's pipes are 8 mm, is there anything else I should take into consideration?Thanks,
Jaco
Jaco are you sure about the 8mm pipe.I know for a fact that Louis only use 10 mm pipe.The low presure inline filter in my case is 10 mm GUD filter part nr BC10
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LouisZ
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Tue Sep 25, 2012 6:31 pm

Jaco, kyk na die Vacuum pyp. Ook op die filters se klamps en ook of die petrol pyp nie geknak is nie. Die fuel filter, die metaal een kan mens omtrent elke 25000-30000km vervang. Die klein blastiek filter is BC10. Altwee filters het rigting op. Die een vacuum pypie vanaf die fuel regulator na die manifold kan ook af wees.
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