Has anyone had this problem?? 1986 2.9L for a while the truck runs fine. I mean “purrs beautiful”! Then out of the blue it starts sounding like it is misfiring, lacks power, won’t rev up, bucks and jerks and blows heavy grey/black smoke. If it stalls it will not start again and smells flooded. Sometimes after I wait a while, it will start and run very rough, but it will only start if I hold it to the floor and crank for a minute or more, then it starts to catch, as it builds R’s and finally starts. And sometimes it won’t start for days!! another thing when it is acting up it seams to loose vacume. I think that because the brake pedle becomes hard to push and I loose stoping power, but it does not affect the power steering.



The code reader says 51 ECT, 54 ACT, 53 TPS & 34 EGR. If I use the reader while the truck refuses to start I just get an endless shrill beep. If the truck is running fine the reader says nothing is wrong but the codes in the computer memory are as above. I have tested all the sensors and checked the fuel system. Anybody got any Ideas ????????????

 

Did you run the pinpoint tests for the codes?

 

Thanks for your help. I 'm not sure what a pinpoint test is or what it involves? I checked the resistance with a ohm metre and installed a new ECT sensor. the problem prosisted and the computor says the ECT is still malfunctioning.

 

EFI or carb?

 

The pinpoint tests are a series od tests that determine the exact cause of the problem. I have all of them scanned except the ECT, I will email them to you if you want them.

 

I had an '86, 2.9, EFI that had the same problem - In trying to chase it I replaced fuel filters and pumps (going through 5 pumps before I finally found the problem), and ultimately rebuilding the entire fuel system to specs. The problem was in the final fuel feed hose between the fuel pump and the engine. The original equipment hose had a small final fuel filter or check valve built into it and this had faulted or plugged.

Replacing it with an exact replacement from the dealer cured the problem for a few weeks but it recurred. The ultimate fix for me was to replace the hose with a straight through. (I used braided HP fuel line hose and double clamped at both ends, but straight through is available (with the proper connectors) if you request it specifically. The final check for me was disconnecting the fuel line from the engine and seeing how freely the fuel flowed with power to the system . . . mine hardly flowed at all until I replaced the line - once replaced, it blew fuel about twelve feet.

 

Ken oo, yes please E-mail the pin point tests thanx Iain


Hand Of God FI

Ray thanx I'll check that hose.
mine is a two pump syst low psi in tank and high psi mounter inbord of drivers side frame rail then it line goes to the fule regulator which is plumed directly into the fule supply rail. is the hose you are discribing btween the pumpand the regulator? thanx Iain

 

That's the line, it connects the high speed pump to the engine mounted regulator . . . the line was a short lived thing with Ford, only being installed on a single year grouping (from '86 to '88 if I remember correctly) then it was done away with. That year grouping was also when they were running a single expansion chamber for fuel mixing rather than individual injectors.

As for the 'two pump' fuel system, they were all that way then, one in the tank, boosting the flow and keeping the High Speed pump primed, and the High Speed pump to maintain the fuel flow at a constant pressure.

 

Ray some may have a single expansion chamber I'm not quit that familiar with these trucks, though I am getting better, mine has 6 injectors I am sure of that. Does that mean it has a a single expansion chamber or not? probally not vital info at this time but knowledge is power an right now I am mighty shy on power thanx for your help Iain

 

with the key on the hi psi pump kiks in but there is no psi at the schrader valve. and I can't locate any kind of check or back flow valve in the line btween the hi psi pump and the fule regulator.
Iain

 

Okay, it's time for a little elimination testing . . . you say you know the HS pump is engaging, but you are getting no fuel 'pressure' at the motor . . . . you're not currently interested in 'pressure' - you should be looking for fuel 'flow'. Even with only partial flow, the system can reach pressure while not running or running at idle. the thing we are looking for now, is fuel delivery - period.

Step one . . . disconnect the fuel hose from the output side of the HS pump. Disconnect the electrical connection from the HS pump. slip a plain hose over the pumps output nipple that is long enough to reach outside the engine compartment (no sense splashing gas on the engine or wiring). The purpose of this first step is to insure your low speed pump is moving fuel. with the hose laying so you can see the end, turn on the ignition and see if you get a fuel flow . . . it may take just a moment to show, but you'll know if it's working. If it is, fine . . . move on to step two. If you don't get any flow, then your problem is most likely either in the low speed pump, or in the wiring or connections to it.

Step 2: if you've gotten a flow from the low speed pump, leave the open tubing where it is and re-hook the electrical connection to the HS pump. Now we are checking the flow from the HS pump. Turn on the ignition and watch the output (just with your eyes) . . . if the HS pump is moving fuel, you'll know it. The pump puts out enough pressure that you should see fuel spurting out to eight/ten feet from the vehicle. "If" you don't get any marked additional power over what you got with the LS pump, then the fault is likely in the HS pump itself . . . if you "get" the high pressure stream you should be getting, then you have another test to make . . .

Reconnect the original fuel line to the HS pump and disconnect it from the engine . . . lay this line out so you can see it and won't soak the engine, and turn the key on again . . . if you still get no flow at the engine, then that hose is the problem . . . if you do get just as good a flow, then the problem is likely in the throttle body or air bypass assemblies or the regulator itself and I have no real skill there.

My only suggestions here have been in attempting to 'diagnose' the fuel supply from the tank to the engine . . . . if the problem is in the engine mounted fuel supply components, my own personal next move would be a stop at the local junk yard looking for replacement components.

 

How about sending this pinpoint info to me also for my 86 2.9 5sp.

Michael