Hey guys I am in need of some assistance here.

I have an 86 F-150 got it cheap me and hubby took apart the engine replaced all the gaskets cleaned it out and put it back together. It was running pretty good. Then the tranny went and we decided to put it in a shop and have it fixed, they fixed it and replaced the fuel pump. It sat there for almost 6 months. I just got it back about 4 months ago problem is I ended up having it towed back to the house because it wouldnt stay started sometimes it wouldnt start at all.

So we replaced the starter and that fixed the starting problem for a bit. Now we are stuck and not sure what is wrong. Everyone keeps saying it the fuel injector problem is there are 8 of them so I doubt all 8 went out at the same time. Anyway we replaced the 02 sensor and it didnt fix it.

Right now it is starting and its staying started longer than it was before it stalls after maybe 5 minutes. Before it would stall 2 seconds after starting it. However it stays started for a long time if the throttle is pushed the whole time. We have also replaced the fuel lines. So like I said we are stuck and not sure what to do becuase the engine was perfectly fine when we finished putting it together and the tranny was just replaced along with the fuel pump O2 sensor and the fuel lines.

Can anyone help us???

 

Sounds like you have EFI in which case, ask the computer what it thinks is going on.

Here's how:

Ford Fuel Injection » How To Run a Self-Test
Ford Ranger/Bronco II EEC-IV Testing

 

I'm not sure I understand what you mean.What is EFI?

 

EFI == Electronic Fuel Injection

As opposed to a carburetor.

Carbureted systems don't have 02 sensors, you mentioned having replaced that so that tells me you must have EFI.

 

oh, yes, sorry, i asked my hubby and he said yes.
he says that he thinks its running rich, so hes going to check the fuel pressure to see if the high pressure pump or FPR is busted.
he also said that while its running he tried to put it into gear, but once its put into drive the engine dies automatically, i dunno if that is part of this problem or a whole different one.

 

How old are the spark plug wires? Replace the spark plugs, wires, distributor cap and rotor....I had a problem just like this on my truck. Bad spark plug wires can cause it to run bad....

I think there is a part called the IAC valve or something to that effect that causes idle and possibly running issues. Never dealt with it directly but I have read about it on here. Cleaning or replacing the part if it's faulty could help.

 

Ethanol fuel can screw things up esp. if sitting for 4 months with no additives.

 

ctubutis,

This strays from the original topic, but for clarity, there are carburetors with O2 sensors. The "feed back" carburetor system used one for the 1984-1986 4.9L engine equipped trucks.

 

That's right. The feedback carburetor system was also used for the 5.0/302 V8 from 1984 - 1985. It had an O2 sensor, MAP sensor, throttle position solenoid, and the EEC-IV engine computer that controlled the air/fuel mixture at the carburetor, engine timing, and emissions components.

 

Another sensor that will cause this exact symptom is the TPS. (Throttle position sensor).

Checking fuel pressure at the rail is paramount at this point, but that's just to eliminate the fuel pump and FPR.

Only way to be sure is to pull codes, otherwise all you can do is throw parts at the problem, and hope you get lucky. Better to ask the computer what's wrong, and fix it according to codes.

EFI can be a dream to work with, once you get used to the system and pulling codes. Get familiar with the following site:

Ford Fuel Injection

Pull codes, and we'll help you from there.

 

Yes, all 3 of you guys are right! Sorry for my brain fart.

 

A couple of items, if it seems to be real rich, check the vacuum line to the MAP sensor. The MAP sensor is located on the top inborad side of the AC casing under the hood. On an 86, I think the vacuum line is a hard plastic 1/4" with rubber hoses on each end. I should run from the vacuum "tree" on top of the intake plenum to the MAP sensor.

You don't say how many tanks it has. In either event, 1 or 2 there are either 2 or 3 fuel pumps. There is the high pressure frame mounted pump and either 1 or 2 in-tank low pressure pumps (one for each tank). If all needed pumps aren't working, particularly one of the in-tank pumps it won't run very well if at all.

Good luck with it and feel to ask questions, that's what we're all here for.

 

Yea, I've read that ethanol fuel has a 3 month shelf life. I alternate using my two trucks just for that reason...to keep the fuel in each one fresh.

 

Thanks guys this helps alot. We had these same thoughts but wanted a second opinion. Thanks so much for the help.

 

so my hubby went out and rented some little computer thing he hooked up to the truck, and he said he tested it and it said system pass. but he said that he couldnt test it while it was running becuz it wont stay running. so now hes stuck and doesnt know what to do.
any ideas?