I bought my 1986 toyota XTRA cab about 2 months ago and was advised that there was a hiccup on acceleration. Truth is it did have a stumble anytime throttle was increased from coasting(driving). The deal is just the other day i was doing 60 mph and suddenly she died, now it will crank, catch and idle for several seconds and die... I know I might have separate issues but I at least need to get her driving again. Anybody interested in handing out some thoughts? It seeems to have good fuel pressure with the pump hotwired because I havent been able to confirm that the pump is getting power normally.

 

Check the rubber tube between the Air Flow Meter and the throttle body. It it is cracked or broken the truck will start for a couple seconds and then stall. It may have been cracked all along causing the stumble on acceleration and finally is cracked to far for the AFM to sense air flow. The AFM has a switch in it that causes the fuel pump to get power with the engine running. Its a safety device that will kill the fuel pump in a accident/ engine stall.

 

This is exactly what my truck would do. Ended up being fuel pump. The pump could be working fine but I believe there is a check valve in pump that's job is to keep pressure in lines. Hence why it'll run for a few second and then die (loss of fuel pressure)

I could be wrong but I strongly believe that's what happened to mine. Because I knew for a fact fuel pump was operating perfectly. At last ditch effort I replaced it anyways and it fired right up.

Call around on prices. Everyone claims they're expensive, but I called around and found one for 50 bucks..

 

Pull a spark plug, if they are a whitish tint that indicates running lean..

 

Thanks for the replies!! I did look for the mentioned hose but not sure whats up but I sure dont see any such hose on my truck! And boosting my fuel pump from the battery sure makes it pump!!

 

Mine did too. The pump was working fine! It was the check valve in pump wore out. Causing loss of fuel pressure

 

Ok I was out out working on my truck again but it doesn't seem like it is that check valve... If I clamp the return hose, it doesn't run any different... And I still would like to here more about that vacuum line from the AFM...

 

I believe superex is talking about the tube (about 3") that runs from the AFM to the Throttle Body. I think it is mentioned on 22re performances website, they will crack underneath near the fan.

 

Thanks guys for the responses! I did take the tube off now and its in mint condition!

 

Is there any chance this could be symptoms of a timing chain jump?

 

This the classic symptom of a COR/VAF problem. To diagnose it, jumper FP to B+ to force the pump to run with key-on. http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump If the truck runs fine then, you've identified the problem.

DON'T drive around with the jumper in. If you get into an accident that breaks a fuel line, the COR immediately stops the fuel pump as soon as the engine stops sucking air. With the jumper in, the pump will keep running, and we will only hear about it on the 6 o'clock news.

 

Tried the jumper, but did not find any difference. Like i said earlier, it runns better with the pump getting juice straight from the battery.

 

does it stay running if you shoot it with ether?

 

we tried running gas into a random hose on the throttle body, and it did stay running.

 

Still convinced it's the fuel pump lol

 

So the only way to make sure of that is to try a different one?

 

Your situation is pretty much identical to the problems I was having. I tried everything. Posted on a few different forums and nobody could figure it out. I jumped terminals Fp and B in diagnostics box and I could hear the fuel pump working great. Finally after running out of options I went ahead and changed the pump and it fired right up. But, if hate to have you replace it with no luck.

-Have you jumped those terminals? Not just jumping it straight to battery. Actually jumping terminals?
-Do you have a fuel pressure gauge?
-Pull a spark plug and take a picture of it and post it
-Replaced fuel filter?

 

I don't have a pressure gauge, and I haven't replaced the filter yet but it looked like I had good pressure so I moved on but I'll have to do a little more fuel work Lol. I have pulled a couple plugs, but I didn't get anything off of them because apparently my engine burns oil. I did jump those terminals but I had better luck boosting the pump straight from the battery, boosting it will actually run for a few seconds but just jumping the terminals it only shorter a little and never actually gets running.

 

I truly do believe its fuel issue.
When you jump the terminals can you hear fuel pump? With just the key on. Not starting it.
Try this!! If you can't hear the pump by jumping terminals and turning key on (not cranking it) then it could be relay or EFI fuse. Give this a try and let me know.

When you pulled the plugs did they have a whitish tint to them? Or are they too fouled to tell?

 

Plugs are too fouled, and I just tried the jumper and didnt get any power to the pump...