1986 5.0/AOD SEFI Hard Start after sitting

[wraithracing]

I have a question for all the EFI experts here on FEP. This is actually my 1986 Bronco with a 5.0 SEFI engine, AOD transmission. All stock and everything is in working order minus the air pump. The vehicle runs very well and generally has no issues. Starts up within a second or two every morning. Runs great with no issues. The problem is that if I drive it and then shut it off, come back to restart after @ 10-15 minutes. The vehicle will crank and turn over, but generally will not start until I do that at least 3 times and or I pump the accelerator a few times. I thought it might be a fuel issue, but honestly not 100% anymore.

I have done a full tune up with new cap, rotor, wires, plugs, oil change and filter. I just replaced the fuel pressure regulator with a new one, but no change. Lift pump in the tank is new, but frame rail Hi-pressure is old/original. I cleaned the throttle body, IAC, and throttle body passages of any and all carbon build up. Still have the same problem.

The vehicle will restart virtually immediately if you shut it off, but let it sit for @ 10 minutes or more and it is hard to restart. Let it sit overnight and it will fire right up. Any ideas, thoughts would be appreciated. I have run out of ideas and don't really want to throw parts at it anymore. I do have a new IAC coming for it, but that will be this weekend before it's installed.

[mudgepondexpress]

leaking injectors? Did you try a clear start (before turning on the key, hold the throttle to the floor and try to start). Time allows the fuel to evaporate, thus the easy start overnight. Quick restart might be faster than the leak, thus making it an easy restart.

Just something I would try next time.

Kenny

[wraithracing]

I had considered leaking injectors and thought about replacing them as preventive maintenance, but just don't really want to have to pull the upper intake and all that is involved. The 5.0 runs pretty well, and only has 96,000 original miles, but leaks like crazy. I have a 351W sitting on a stand that is just itching to be swapped into the Bronco . . .

I will give your suggestion a try. I think I tried it awhile back and there wasn't much of a difference, but I will try anything right now in hopes of getting this sorted out. Thanks!

[Jerry peachuer]

Air in fuel system maybe
Try removing gas cap next time or purge the Schrader valve easy to see if air eeks out or fuel
Also fuel filter element could be floating around freely inside filter body when it should be glued in place internally

Just some ideas

Pumping accelerator I don't think will do anything its injected

Turn key forward a few times before full crank to see if it is a pressure issue
Only thing changed is ethanol fuel sounds like

Give it a spritz of starting fluid to see if it takes off or if it keeps cranking

[OX1]

I have a question for all the EFI experts here on FEP. This is actually my 1986 Bronco with a 5.0 SEFI engine, AOD transmission. All stock and everything is in working order minus the air pump. The vehicle runs very well and generally has no issues. Starts up within a second or two every morning. Runs great with no issues. The problem is that if I drive it and then shut it off, come back to restart after @ 10-15 minutes. The vehicle will crank and turn over, but generally will not start until I do that at least 3 times and or I pump the accelerator a few times. I thought it might be a fuel issue, but honestly not 100% anymore.

I have done a full tune up with new cap, rotor, wires, plugs, oil change and filter. I just replaced the fuel pressure regulator with a new one, but no change. Lift pump in the tank is new, but frame rail Hi-pressure is old/original. I cleaned the throttle body, IAC, and throttle body passages of any and all carbon build up. Still have the same problem.

The vehicle will restart virtually immediately if you shut it off, but let it sit for @ 10 minutes or more and it is hard to restart. Let it sit overnight and it will fire right up. Any ideas, thoughts would be appreciated. I have run out of ideas and don't really want to throw parts at it anymore. I do have a new IAC coming for it, but that will be this weekend before it's installed.

My dads LTD still does this. Very specific amount of engine warm up and then heat soak, right around the same timeframe.
Couple years back, I swapped out EVERYTHING. 2 new/used computers, new quarterhorse (reloaded files several times), new distr, 1 aftermarket TFI and one new Motorcraft TFI modules, an entire new remote TFI setup, new adj FPR, new spark plugs/wires, new IAC, new TPS, even new O2 sensors. I only did all that after extensive sensor checks and datalogging turned up nothing. I have wideband and fuel pressure guages in the car. Have done extensive datalogging on 1/4 horse and directly off breakout box on various sensors and an automotive fluke meter that measures min/max over an extended timeframe.

One thing that did help was voltage to EEC. I was only losing about .04-.08 volt from battery to break out box. Would think it is no big deal, but running larger guage wire to EEC main power helped a lot. It still does it sometimes. Very annoying when I just need to go get gas in warmer weather, as that is jsut about the right timeframe for it.

[OX1]

leaking injectors? Did you try a clear start (before turning on the key, hold the throttle to the floor and try to start). Time allows the fuel to evaporate, thus the easy start overnight. Quick restart might be faster than the leak, thus making it an easy restart.

Just something I would try next time.

Kenny

Pretty sure even the truck 5.0's still had schrader on fuel line. Just get a cheap screw on fuel pressure guage, see if it leaks down real quick.

[ZephyrEFI]

Pretty sure even the truck 5.0's still had schrader on fuel line. Just get a cheap screw on fuel pressure guage, see if it leaks down real quick.

Yeah, this. I have a gauge permanently mounted on my rail. I've had to fight bad regulators AND bad leakdown valves in the pumps.

[wraithracing]

Thanks for all the ideas, I will give them a try this weekend if possible. We are supposed to get a cold front tomorrow and drop us out of our nice 50 degree days. My F250 is in the garage waiting for me to swap transmissions since the original one finally shot craps after 250K miles. Fun times for sure!