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86 Ranger bucking issue


Joined
Feb 17, 2010
Messages
22
Vehicle Year
1996
Transmission
Manual
Hi everyone,

I've been trying to fix an issue where my 2.3l FI engine bucks when under load. You can drive it around at 50-70% throttle alright, but if you apply any more throttle the engine bogs and bucks violently. So far I've done the obvious things, new plugs, wires, coil, Fuel filter has flow, and the vacuum is good with no leaks. The cap and rotor were done 16k ago. I'm kinda scratching my head here. It will drive better for the first 30 minutes then the throttle issue gets much worst, especially on any sort of incline, to the point where it will struggle to maintain safe highway speeds. I'm fairly certain both pumps are operating correctly. It also idles quite rough. Any ideas? I'm worried it might be an actual lower end or engine issue or bad rings since the problem seems to worst as you drive it. Thanks!

Andrew
 
Sounds like the fuel pump is going south. You would need to check the fuel pressure under load to see if it is dropping on you...how that is done is another story...

Always a video somewhere...

http://www.youtube.com/watch?v=poS2K9VdTR8

Now, the 86 Ranger does not have the same psi fuel pressure as the one shown in this video...92 was around 35 psi so I'd imagine the 86 is somewhere thereabouts...not sure if I'd recommend this method...you might have someone help you with the filming if you are going to do that...or to just see if the gauge drops under load...meaning your pump is going...
 
Last edited:
I suspected a fuel pump issue. I just wasn't sure because of how the engine would always run rough but the bucking issue would get worst as the drive went on. I'll run a check tomorrow, but I guess it would probably be an issue with the high pressure pump not providing enough pressure to the rail at the higher throttle settings?
 
Could be either one, actually. You may need to test both for that matter. Could even be the sock in the tank is partially blocked but not likely. I've had fuel pump issues in the tank before and they gave the same symptoms...bucking like crazy and sporadically...until it wouldn't start.

Anyway, testing is the only way to determine the next step to take. If it is the fuel pump on the rail it's much easier to fix than the in-tank one...
 
I would check pressure & delivery volume. If either is lacking, your engine won't run right. Starvation while under load will cause the symptoms described. With the age of the truck & tank, I would suspect that the sock might be getting a bit blocked.
With a carb'd engine, you could run partway up the hill with no problem, but the level in the bowl would be dropping slowly as the fuel was consumed faster than it was being supplied. In that case it was the sock. I removed it and put a handily accessible filter under the hood to protect the carb from 'stuff', problem solved.
From what I understand, the lift pump {low pressure} in the tank fills a canister on the frame rail that has a filter cartridge, which is what I think my 85 EFI has. The canister forms a sort of 'buffer' fuel supply to the high pressure pump mounted a bit forward, about under the drivers seat. In later modes, the canister filter was left out and a filter placed elsewhere, but the canister was left to be an 'accumulator'. I think.
If the low pressure pump is dying, or the sock is plugged, fuel flow might not be adequate for high speed operation. I would do a delivery volume test for 5-10 minutes to see if it can pump enough fuel.
tom
 
Good point Tom...I had a electric pump on my carb and it seemed to be pumping fine...until I did the volume test...it was just a trickle coming out the end of the hose...

When new, that same pump, even though it was only rated for up to 7 psi, would pump a good squirt all day...I forget the rating in gallons per minute though...but the flow should come out the full diameter of the hose on a properly working pump.
 

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