Again:1994 F150 2wd 5.0 Automatic:Starts hard when warm after getting to operating temp then let to sit for 2-3 hours-it turns over about 3 times longer than it used to, 3 times longer than it does stone cold, it runs great with no missing, or roughness at all, took it to an independent shop they found no codes they say they used a Sun brand diagnostic computer, they say this is one I'll have to start throwing parts at to fix, which I find unacceptable, does Ford have a better, more complete computer hookup that is unique to Fords which could find this problem? or do I really have to start throwing parts at it? the problem seems to be getting worse, please help me before I get stranded somewhere, Thanks!!

 

Computer codes are electronic parts in that system, it will not tell you if fuel pressure is low or if other mechanical problems exsist. You can give us maybe more history on the problem and/or maintenance you have done & we might be able to help.

 

This problem came on suddenly, it was just after a gas fill up, I first thought I'd gotten bad or dirty gas, I just changed the fuel filter, and have run two more tanks of gas through it, and no change, back less than 1 year ago (10k miles) I completely went through everything tune up wise from filters to plugs,wires,cap,rotor,ect,ect, truck has always run great even before I went through everything,I've owned the truck for about 15 months, gets a solid 15 mpg around town with a/c on, it will start right up after a brief shutdown,like say going into a store for a half hour, and will start right up after sitting all night or all day at work, the only time it starts hard is after sitting for 2-3 hours, this is when it just turns and turns and turns before starting.
It doesn't make any difference what tank I'm using either.
Thanks for any imput as to where I should start throwing these parts would be great.

 

if your vehicle has set for even 2 hours id say it should be dead cold. the only thing that i can think of that might not be where it would be when its been setting all night would be the fuel pressure. when you start your vehicle do you turn the key on and wait for the fuel pump to build up pressure before you start it? you could also try unscrewing the gas cap before you try to start it and see if there is pressure there or a vacuum. maybe you have a semi plugged fuel return line.

 

OK, I'll try removing the gas cap before starting, and how would I check for a semi blocked return line? Thanks!

 

If it is starting fine in 20 to 30 min after shut down, hard time starting after 2 or 3 hours but starts fine after 5 or 6 hours, the truck could be flooding. I had a T-Bird doing a similar thing at one time. Turned out to be a fuel pump relay sticking closed and allowing the pump to run after shut down. The return lines were taking care of most of the fuel but some was still getting into the cylinders and flooding.

Sounds about like the same problem.

 

The fuel pump relay sounds like it could be it.
Is there just one relay for both tanks/pumps? because it does the same thing on either tank.
where would I look for the relay on my '94, I'm thinking of starting the parts toss there!

 

There should only be 1 FP relay and I think it's under the hood on the passenger side fenderwell. Normally, it's in the 'distribution box' which is a rectagular box with a cover on it. Once you find it, there should be multiple relays in there.

When you turn the key to the 'on' position, do you hear the fuel pump run for a couple of seconds?

Mike

 

Relay is in power supply box near air filter or plugged into wires nearby. I'd get a pressure gauge at parts store for ~$40 and follow instructions. Your pressure regulator could be off or other problem may show up. If it checks fine, I'd recheck when she didn't start. I'm thinking your problem is more likely in the electronic ignition. It's definitely not out but when warm may not operate properly. Checking the fuel pressure could lead to other alternatives. The owner's manual will show which relay is for fuel supply, look under fuses/relays. Make sure the small ground lead from battery terminal is okay as well, yellow wire I believe. Diagnosing problems like these are difficult. I've spent lots of $$$ changing wrong parts before. More likely it will get worse and be easier to solve later but you may not be able to risk getting stranded and patience sometimes leads to more frustration. Good luck.

 

Guys, The starting problem got worse today, after sitting all day at work 8 hours it just cranked and cranked until it finally started, so I pulled out the owners manual and looked for the fuel pump relay, and you're right there are 4 relays inside the power distribution box and a space for a 5th one, they are all marked with nimbers 1-5 but don't say what they relay power to, and in checking in the manual it shows them but doesn't say what any of them relay power to either.
On page 362 it shows the power distribution box, and on page 363 it tells that location number 9 is the fuel pump relay coil/powertrain control system, and number 16 says fuel pump feed, does anyone know what relay number is in fact for the fuel pump?? shouldn't be long now until it won't start at all. Thanks!!

 

Are all relays the same #? If you think the relay itself is bad, you can switch or pull one at time to try to isolate which one is bad. I would still check fuel pressure. Gauge does not cost much and testing is not hard. It will not mean that a pump is out, if you have low pressure, but if the tests are okay then the fuel system "should" be okay. When you turn the key on, do you hear the pump run? You can pull the Schrader valve on passenger side fuel rail and turn over the engine. Fuel should come out (if you don't want to use gauge but be careful not to let gas ignite).

Relay #5 is not used. Relay #2 is fuel pump (ref. Haynes #36058, p. 12-3) Fuses (power distribution box only) are: #9-EEC system, fuel pump relay coil. #16-Fuel pump feed.

I would check EEC (computer) for codes (scanner < $25 at WalMart or most parts stores) before suspecting electrical problems and do the fuel pressure check with gauge before assuming the problem is in the fuel supply system. How do you know that your ignition is firing? I've known a few with this sort of problem changing fuel filter, pumps, ignition coil, distributor rotor/cap, then fixing problem by changing computer because it was not supplying power to the ignition module.

AS for testing a clogged or restricted return line, there is a test with the gauge that checks for proper function of the regulator. If the pressure is high then you'd suspect a pinched or restricted return line. I could go through the tests but it is all in the Haynes manual referenced above and others and the fuel gauge instructions. You just use the proper adapter and thread on at the Schrader valve mentioned before and turn the key on/off for some tests, crank engine for others. You also watch to see if pressure drops within too short of a time after killing the pumps. If you want I can go into more detail. If you are determined to fix the problem without the pressure tests, I'd rather not go through all of it. You can fix the truck by "throwing parts at it". I've done that and I know of others but more likely you'll spend more than the cost of the gauge before you find the cure. I'm also hardheaded and I really do wish you luck. I've been through this myself but by no means am I an expert. Nor is my ego large enough to think anyone has to do anything my way. I'm just trying to save you some of the frustrating experiences, I've already been through.

 

sounds like something i need to do tim, think i'll get myself one. not like you're just going to throw the pressure gauge away after your done either.

 

does it fire, chug or try to run when you turn it over cold or do you just hear the starter running?

 

Just the starter turning the engine, no chuging, no fireing, for the longest time until it finally fires, and BTW if I had only turned one more page in the owners manual I would have found the location for the relays indicated, the fuel pump relay is in the number 2 slot, so I am going to swap it with my number 4 which is for dual rear wheel running lamps and trailer tow lamps, and since I have no dual rear wheels, and am not currently using my trailer towing lamps I should be able to then eliminate the fuel pump relay as my problem.
I was thinking back, and a couple of times after this hard start I thought I smelled gas, thought I was inagining it but now I think I really was.

 

sounds to me like your not getting gas. next time it does it you could try spraying some carb spray past the butterfly valve of the throttle body and then try to start it.

do you turn the key and wait for the fuel pump to build up pressure before you start it? do you hear the fuel pump build up pressure before you start it? do you keep your foot off the gas while you are cranking it?