Hi all,

I need a little help diagnosing an annoying problem. Whenever I go to start my truck, if its been sitting for more than just a couple minutes, it'll start up and immediately die on the first try and then start up and run fine on the second shot. When it dies it seems like the idle just drops way too low to keep running. Its not a crippling problem, but its embarrassing when I show the truck off to my friends. Any ideas would be appreciated. My battery cables are a bit frayed and need to be replaced. Could that be the issue?

John

 

Mine does the exact same thing, although it's never been enough of an issue for me to care. My electrical system is mostly new, so I doubt that's the problem. What year, engine, et cetera is your truck?

 

I'm more familiar with injected engines, but same principal here. You're losing fuel slowly. Doesn't sound like it's leaking out of the carb because it runs just long enough to burn that fuel off. When you start up is there puff of smoke or rich smell from that first burst out the exhaust?

If you press the pedal up and down once, or hold down while cranking does it make a difference?

My bet is there is a failed check valve or leaking fuel line somewhere between your tank and fuel pump that is either leaking gas out or letting air in.

 

The truck is an 86 f-150 4x4 with the fuel injected 5.0 Liter V8.

 

A couple questions that show my ignorance. What's a check valve? How do I find out if ones bad?

 

If it's a 1986 with EFI and the engine is acting up, ask the computer that controls it what it thinks is happening.

Here's how:

Fuel Injection Technical Library » How To Run a Self-Test

 

Oh, it's EFI? That changes everything. Basically check valve goes in line of the gas flowing. Like the thing you have to squeeze to inflate a beach ball. Lets fuel flow to the engine, but not back to the gas tank.

What happens is you are slowly loosing fuel pressure when the truck sits. My two best guesses are this: Either a leaking injector or a bad fuel pressure regulator. If it's an injector take the spark plugs out and see if one is darker, or wetter than the other. For the regulator, if it was a rubber hose on the side leading away from the engine, pinch that line off with vice grips and let the truck sit. If it starts fine like it does cold then bingo.

Like Dorsai said, fairly easy to diagnose, but sometimes not worth the $ to fix. How does the truck run at idle? Does it ever hesitate when you mash the gas? Does it seem to momentarily lose power on the highway?

Assuming you have an electric fuel pump that runs when the key is on, trying turning the key to run for a few seconds before cranking and see if that fixes your problem.

 

I have been messing around with a 86 ranger with a fuel injected 2.9, basically the same thing as you have only missing two cylinders(same computer system). I never had any codes, but it would not run very well at all when it was given to me. Everything I did helped, and i recommend you do the same after you check for codes. I believe now I finally have got it.

1. The first thing I did was give it a good tune-up. New sparkplugs, wires, cap and rotor.

2. I then started poking around the throttle body. I found the EGR passage was totally clogged with gunk. I also cleaned around the throttle blade and the idle air control motor.

3. I then started playing with the idle screw. I unplugged the idle air control motor, started the engine, and set the idle screw till it barely idled, and the plugged it back in and tried it. You are not supposed to mess with this screw, but sometimes you have to. It got it where it would run half decent, but it still had a rough idle and was easy to stall out(it's a 5 speed).

4. Last thing I did was check the timing. Wow, it was way off. I put white out in the spot on the damper scale where the sticker said it should be, and then loosened the dist bolt, unplugged the spout connector, and the set it(mine is supposed to be 10 degrees). This made the biggest difference, I do not know what previous owner was messing with it, but it cleared everything up.

 

I have the same problem and my only codes are EVP sensor related. I can't see the egr affecting the fuel system. I have leaking injectors and I believe this is the problem, but in this case "asking the computer what is wrong" doesn't accomplish too much. I spent a lot of money diagnosing and fixing EEC-iv error codes and still have problems.

 

I have found the EGR can be a little bit leaky, and this will cause a rough idle and stalling. To test them, most of the time I make a metal block-off gasket to block it off and see if it clears up. On this engine, it didn't clear it up, but I left it blocked for a few weeks. I started having a little bit of pinging problem, so I took the block off gasket out, and it accelerated much smoother with the EGR connected.

 

Nobody said to "ask the computer what is wrong," I suggested to "ask the computer what it thinks is happening." Big difference.

There are some failures the computer won't necessarily know about and can't provide direct help with, but it's always the first step in diagnosing any computer-controlled engine.

 

I apologize for misquoting you. And I agree that a code reader is a tool that can help diagnose a problem, but it can also lead you in the wrong direction. When you spend $500+ fixing the error code and the problem persists. I was lucky because I watched my father with the assistance of the local ford service department fix and replace parts to eliminate all of the error codes. That was 20 years ago. The truck still has the same problems. I know not to take what the code reader says as a definite answer, but alot of people will sit there and throw money at these things and not get anywhere. I wish there were a better way. I didn't intend for my post to sound like a challenge of your advise, I was irritated because I have been hearing the same thing for too long.