Hi All.
Let me start by saying I have a 88 F150 w/ 300-6, farm truck/wood hauler. I depend on this truck desperatly, I've owned it for 12 years and it has much senimental value.
Anyway, lately after I've driven it for a few miles, done chores for 15 minutes or so, I get back in and it won't start? Turns over, but not sure if I have no spark or no gas, it seems to happen when I don't have any tools. However, if I wait a couple hours, I go back and it fires right up.
Last week I installed new coil, ig. mod., plugs, wires, dist. cap and rotor. After installing all that, I was certain to have found the culprit, wrong!! Today it took a dump on me after my third 2 mile trip, came back a few hours later and it started right up and took it home. I now don't dare take it anywhere.
If it starts, it seems to run fine, any ideas??? Fuel pump/filter??
One more thing that might be a clue is sometimes when trying to start it, it turnes over for a couple seconds and will start if I touch the gas?? Could it be flooding itself?? Also, when I start it after sitting overnight, it starts immediatly.

 

I have also HEARD OF the ECT causing this...

I have never run into it myself though.

Something to look into.

 

Thanks,

I'm not sure what a ECT is??

 

Engine Coolant Temp, go to fordfuelinjection.com, and you can get the resitance specs for it, and test it. Id check it and also, the MAP sensor.

 

Are you lightly touching the gas . Next time put it to the floor and see if it starts. I am assuming it is fuel injected.

 

As soon as I notice that it isn't going to start immediatly(a couple seconds), I put the petal to the floor and it usually spits and sputters but will start. My problems I'm having are only when the engine is warm. It is fuel injected.

 

check battery cable and engine to frame ground and any other ground you can find.

 

When you put the pedal to the floor during the cranking mode the computer thinks that it is flooded and makes the adjustments .My guess it would lean out the fuel mix.Maybe some of the other members would know for sure.So is it possible what ever the problem is that the vehicle is too rich on startup because the computer is gettiing bad infomation from a sensor.I would check the ect sensor.

 

My guess is that it is putting out to rich of a mixture and flooding out. Last Sat. when it happened, it rolled over for a few seconds, I hit the gas and it popped but didn't start. After that, it wouldn't pop at all and assume it was flooded?? Then like I said, I came back a couple hours later and it started perfectly. Does the ect sensor regulate the fuel mixture depending on the engine temp????

 

If the EEC-IV detects WOT (wide open throttle) during start, it will shut off the injectors. Here's a test that sounds scary, but worth trying. While the engine is cold, before you hit the starter, floor it, then try to crank it. If it cranks, (obviously take your foot off the throttle immediately) then go call the parts house for an injector servicing kit. With the injectors shut off, the engine should not crank, cold or hot. There's a little rectal pucker factor when you first hit the starter, wondering if it is going to fire and send your 302 into orbit.

Sounds like you may be dumping too much fuel in when it's warm, but perhaps AFTER you shut the engine off. Before you start digging in there for the ECT (not the easiest thing to get to), go get a pressure gauge that's good up to 100 PSI and check the fuel pressure. If the fuel pressure regulator isn't working right, or if there's an obstruction in the tank return line, you'll over pressure the injectors. Good time to do a leak-down test as well. While the engine's cold, connect the gauge to the schrader valve on the fuel rail. Turn the key to RUN, but don't start the engine, and jumper the DLC Pin #6 to ground (Fuel pump RUN input) and see where the pressure goes. The 2 second priming run at KEY ON is not enough to build full pressure. Mine only went to about 20 PSI when I turned the key on. With the pump running constantly the pressure should be 40-45 PSI. Turn the key back off, and see how long it takes the pressure to bleed back down. After 30 minutes, I still had 10 PSI on mine, but this may vary with age a little. If you have a leaking injector (fouled with crud), it'll leak down much quicker. Use the high pressure for the test. After you check for pressure and leak down, crank the engine and let it idle. The pressure should be 30-35 PSI. Pop the throttle, and the fuel pressure should spike to 40-45 when the intake vacuum drops. Let the engine warm up, repressurize the fuel rail with the fuel pump test, and run the leak-down again. If there's any difference in the leak down cold/warm engine, I'd guess at a wonky injector. There's only 8 of 'em, and if you're as lucky as I am, it'll be #2, #3, or #4 (under the plenum). If these tests pass, though, yep, possibly an ECT. It sounds to me, though, like it may be flooding after you turn it off, which would again point back at the injector(s). If an injector's fouled, you'll normally have only part of the cylinders running rich (one for each fouled injector) but the EEC is going to be trying to compensate and lean them all back. Here's a couple questions to visit. Have you had any pinging or sputter under heavy throttle? (one or more cylinders too lean) Have you noticed any black smoke from the tail pipe? (one or more cylinders too rich) Is there a lot of black smoke when you manage to crank it with the little trick you described? Is there heavy soot deposit at the end of the tail pipe?

Next question, if you shut it off after it gets warm, and IMMEDIATELY try to restart (within 10 seconds of turning it off), do you get the same symptoms? If so, well, we're back to the ECT. It's about $15 from Advance Auto Parts, and doesn't take long to install. You'll want to take off the hoses between the throttle body and the air filter. I think I used a 1-1/16 deep well socket.
Some say to drain the coolant down, but I didn't. Just wrap the threads of the new one with Teflon thread tape or use your favorite pipe sealer, and have it close when you get the old one out. Make sure there's no pressure in the radiator (loosen the cap and pull it off) Back the old one out after you loosen it and poke the new one in quickly. I don't think I lost more than a teacup full of coolant. Plug everything back up, and warm it up to check for leaks.

 

Thanks Guys,
Wow thats alot of great info, I really appreciate it. In answer to OLD PAINTS questions.
I havn't had any pinging, black smoke or any soot at the tail pipe, once it starts it seems to run as it always has.
I cant answer your other question about restarting it immediatly after it gets warm because every time its done it its been about 15 minutes or so til I get back in to leave. I'm very curious to see if it would. Tommorow afternoon I will take it out for 10 miles or so and try that.
One thing I didn't mention was I squirted starting fluid down the throttle body last Sat. when it was't starting to see if it would pop and it wouldn't. This was about all I could try with the tools I had at the time.
If after driving it tommorrow it doesn't start, I'll pull a plug and see. Honestly, I'm hoping that it won't start, so maybe this problem can be found!!
Again, thanks for all the info. and I will let you know tommorrow night.

 

After rereading your post again, I realized I forgot about your first test you told me to try. My curiosity got the best of me so before I went to bed tonight, I went out to my truck, floored the gas, turned the key and it did fire right up. I tried the same test with my other truck and car and your absoluty correct, they wouldn't start. I'll still take my truck out tommorrow and let you know about an immediate restart after its warm.
Thanks again

 

Check your fuel pressure regulator. It's on the fuel rail and has a vacuum line on the top of it. Pull the line off it's wet or you smell gas there then it's shot.

 

Yup, sounds like a busted FPR to me. With the residual pressure in the fuel line, if the diaphram in the regulator is shot, it's probably forcing fuel back into the plenum. If ya lived in AL, I'd give ya the one I pulled off my truck last weekend. Was working fine when I ran the fuel pump tests. I'd already bought a new one, so put it in anyway. But, just to make sure, go get the pressure gauge. You won't regret it. I think there are some kits out there that have adapters for both compression testing and fuel pressure testing. I just got a fuel pressure gauge kit with dump valve and drain tube setup. That, and a vacuum gauge told me more about my truck than all the code reading.

The injectors are a lot harder to get to, so change the FPR first. It's not real bad, just some awkward angles to use an Allen wrench, and you'll have to get one of the screws usinig 'feelavision'. No need to disconnect any lines or anything. Take out the three screws, pop the old one off, new one on, put the three screws back.

If you find you have injector problems, go ahead and be prepared to change the plenum and throttle body gaskets. It seems, so I found out the hard way, this is a common failure point on the 5.0L. I didn't keep the number, and I'm away from home right now anyway, otherwise, I'd give you the exact Felpro gasket set to get. I just did the plenum job last weekend, as well as new O-rings on all the injectors. Total cost of parts was only about $20.

Good luck, and hope we got ya on the right track.

 

Thanks guys,
If my Fuel Pressure Regulator is shot, would I notice any change while I'm driving?