Hi,

This is my first post here, not sure if I'm supposed to jump right in or give an intro. so please let me know if I'm out of line.

I just bought an '89 F-150 (4.9L I-6) pretty cheap cause it's owner needed to unload it quickly. It had been sitting for the last 6 months or so, not running. The owner claimed that it had run out of gas and couldn't restart it, so he had it towed home and then never got around to fixing it. The owner's wife (a co-worker of mine) told me that until it died on the road on him, it ran fine......well at first it wouldn't start so I set about trouble shooting the problem.

I put fresh gas in it (the tank did not seem to be empty) and cycled thru the key switch a few times to get it pumping. Pushing the schrader valve indicated that I had fuel pressure. Strangely, the fuel pumps stay running with the key in the on position...they don't shut off after 2 seconds as usual..... I checked for spark and had none. I replaced the Ignition Module with a "known-to-be-good" spare...now getting spark at the coil (kinda weak) but none at the wires. Went ahead and replaced the coil, wires, cap, rotor and fresh plugs (old ones were well worn). Now getting strong spark at each wire! But still won't start...checked the injector signal with a "noid" light and it checked out. Figured I might have flooded it, so I waited a couple of hours and tried again...still no-start. I gave it a couple of shots of starting fluid and it fired right up and runs strong and smooth but will not hold an idle for more than a few seconds before it dies....if I hold my foot on the gas at 1500 rpm or so it stays running though. If I shut it down and try to restart, it won't unless I give it a shot of starting fluid (but once it starts it will stay running, not just burn off the fluid)

So my problem is a) Why won't it hold an idle? and b) Why can it only start with the aid of starting fluid? I'm guessing these are related problems, but I'm stumped.

Thanks in advance! This site is great!

Chris T

 

sounds like you got a massive vacuum leak. Check all your vacuum hoses and replace any that are missing or bad.

All that extra air is making your mixture too weak and you need a boost of EXTREMELY FLAMMABLE MATERIAL to get it going.

Go very easy on the starting fluid. It's ETHER and IIRC about 5-7 times more volatile than Gasoline. It WILL blow holes in your pistons if you're not careful.

 

Your fuel pumps continuing to run after 2 seconds could be a clue to your problem. You may not have sufficient fuel pressure. I would suspect any of 3 things: the in tank fuel pump, the high pressure fuel pump along the frame on the drivers side, or the fuel pressure regulator. If you don't find any vaccum leaks as the first poster suggested, I would consider getting the fuel pressure tested. Keep us posted. Good luck.

 

Take the Idle air control motor off and clean it or better yet replace it. Clean the throttle body passages while your are at it.
Once you get it running I would run a couple of cans of seafoam thru it also. Good luck

 

Exactly. I would be looking at the fuel pressure regulator. Test the fuel pressure and see what it has. You could try blocking the return line and see if the pump runs for 2 seconds and then shuts off at start up.

 

Check your throttle position sensor, we had the same trouble with his truck years ago. Seems that with the TPS being dead the computer wouldnt inject any fuel, but if we would introduce some sort of fuel (starting fluid, WD-40) it would fire and the computer would go ahead and take over. We put a new TPS on it and it worked fine. Good Luck.

 

Chris, find my last post and read. The problem is whatever is causing the pumps to continue running. I've been trouble-shooting my 89 I-6 since oct. and still looking for a reason why the pumps want to run. It runs fine if they shut off normally(rarely)Let us know what you find.

 

what is seafoam ,never heard of it?

 

Thanks for all the replys. I tinkered with it some more today. Let it warm up to full operating temp and after that it would hold an idle, just not a smooth idle, it would also restart. Cleaned IAC, chased all vacuum lines and found no leaks. I did actually manage to drive it a bit, it seriously bogs under load and generally runs rough...once I get the throttle past a certain point, it wants to stumble and quit.

I will check the fuel pressure and report back, what should it be ? I'm also going to check the TPS and MAP sensor.

Thanks again,

Chris

 

Have you checked the Fuel Filter yet?
A clogged Fuel Filter is likely to happen after running the tank dry, then when he filled it back up from a can, it would still not want to start.
I had one clogged on another vehicle, and it would idle, but not run above 35ish, and hard acceleration would stall it out.
That should also explain why the fuel pump is staying on, because the pressure doesnt get high enough to shut it off.
Thats also why it will start on starting fluid, because it doesn't have any gas, once it runs, the vacuum is high enough at 1500 rpm Wide open throttle to let it idle.
You know the fuel pump is good b/c you can hear it.
If you have a fuel pressure gauge to attach to the schrader valve, you could probably watch it go up as you turn the key on, then down as you crank/start it and the pressure cannot keep up with the demand.
Be carefull that you have the right tool for the fuel filter, though i have heard stories of different years having different tools.

Good luck.

<edit>
normal fuel pressure for Fuel injected engines should be 39-40psi under normal operating conditions, and approx 30psi at idle or other high vaccuum. If it drops lower than that durring load, than its probably the filter.

 

Fuel pressure does not turn the pumps off. They run for 2 seconds or so when the key is first turned on, and then shut off, regardless of what pressure may be in the lines. Either the relay is sticking on, or there is a fault to power somewhere in the fuel pump wiring. That's the only things that would let the fuel pump stay on. I think the 6 cylinder fuel pressure should be higher too, around 55 with the engine off, 45 at idle. Have you pulled the codes? If you haven't that should be high on the list of things to do. I'd also check ignition timing to make sure it is set correctly. I'd also definitely check the tps - you should have approximately .9V with the throttle closed, and it should increase smoothly up to about 4.8V at WOT. Also check the idle air control valve to be sure it and the throttle body are clean.

 

Still working thru this as time allows:

Replaced TPS, ECC Relay and Fuel Relay, Fuel pressure is 57 with engine not running, 51 with engine running. Forgot to mention before that check engine light is on. Tried to pull codes both thru the check engine light and using a meter. I cannot get any codes....the needle doesn't move at all (checked meter for correct function)

I'm wondering if the ECM is bad....but didn't think it would run at all with a faulty ecm......and ideas?

 

I had a computer not go into self test mode, and the truck wouldn't start hot. That could very well be the problem. See if you can find a place that will test your computer to see if it is indeed the problem.

 

Well, I replaced the ECU with a reman'd one from Autozone and it cured my problems. The fuel pumps now shut off as they are supposed to and it starts and idles good. Got a few other issues to address before I road test it.

Thank you for the advice!

 

No start without ether. Cold idle good, fast idle warm. Driveability great. Town,highway interstate. Runs out like a 5.0 should. Hard crank when warm. Fuel filter clean. Plugs, wires and ignition all good. Runs like a champ, once it starts.