I just bought a 96 f-150 with a 5.0, 5 speed standard. It starts great cold and great when it is hot up to a couple min after you shut it off, after about 15-20 min it cranks over for for 5-10 seconds before it will start. I checked the fuel pressure with the engine cold it is 38 psi and 34 psi while running. I haven't check it warm yet. I noticed that the coolant guage in the cab is pretty cold when the truck is warm ( around the C mark) but the heater air in the cab will burn your hand. Could it be a bad ECT? Any suggestions would be great thanks.

 

Is it throwing any codes (check engine light on)? I believe there are two ECT sensors. One for the computer, and one for the dashboard. Someone correct me if I'm wrong. If the computer is getting the wrong temp, it COULD cause a hard start scenario by affecting timing. Did you check the fuel pressure on the rail by the injectors? I changed my fuel filter shortly after I got my 96 about a year ago, and whatever came out of it looked more like swamp water than gas. I'd say change your fuel filter and go from there. You will need a special tool, but its not really all that hard. If you have access to a scan tool, hook it up, and see what the computer says the engine temp is at. If you don't have one, check out harbor freight. They have one for about a hundred bucks right now...definitely worth every penny.

 

Yeah I checked it on the fuel rails. I have no codes, if i do a koer test it comes up with a p0411 ( air pump). My fuel psi gauge does go down very slow after I shut the engine off, Is there a rule for time vs psi drop ? I changed the temp sensor for the ecm ( i found out there are two diff sensors) and no difference. The longer i let it sit the harder starting it gets to a certain extent. Example if I let it sit 10 minutes it starts allot better then if I let it sit 30 min. When it does finally start it puffs a good black cloud like it was flooded.

 

I hate to say this, but you might need to figure out whats going on with the smog pump first. The pump only turns on under cold start conditions to help with emissions. The engine gets a VERY rich mixture and extra air is introduced into the exhaust manifolds (at the very back) and creates sort of an afterburn to heat everything up quicker (including the cat). With a bad ECT for the computer, it could be turning the smog pump on, giving a very rich mix, AND affecting the timing. Only when the engine cools off enough to make the altered timing close enough will it fire up....sounds plausible in my head. lol. Double check to make sure thats a good sensor. If you have a scan tool that can show you live data, it will make that job much easier. Otherwise, just backprobe the senor and put a voltmeter on it.

 

Installed a set of eBay re-manufactured injectors, the problem seems to be fixed. and way more throttle response now.

 

I also have a 96 with a 5.0, and I'm having a very similar issue. Except I've noticed that it is only a problem when I attempt to start (warm) on the front tank. Calgary, do you have dual tanks? If so, can you remember if your problem only occurred when a certain tank was selected? Thanks for following up w the injectors solutions, btw.

 

I just have a single tank, the injectors where the cure for mine. I just put a fuel gauge on the rail and then pressured the system up. I used hose pliers and clamped off the supply then return then both and watched my fuel psi . Th fuel psi kept dropping as it sat, so that only left the injectors as a problem. ( I clamped the lines off with the engine NOT running)