Is it possible that my EFI on my 1996 F350 7.5 is bleeding off the fuel from injectors over night? When starting after sitting overnight, it runs very rough, until it warms up. Usually 10-12 minutes, it is not throwing any DTCs, except once a Random Misfire code because I got pissed and revved it up pretty hard. It also is intermittently misfiring at freeway speeds, and then clears out and runs smooth for 50-60 miles, no pattern, just random miss. Am now in Texas, and am going to head back to California in a few days. Thanks! Dale

 

That would not be uncommon and it's not usually a problem since the pumps can easily repressurize the system before startup, it would be a bigger issue if it bled off in minutes or immediately after shutdown, that could indicate a problem that the fuel pumps would have a harder time overcoming. Get yourself a fuel pressure gauge and have a look.

 

The check valve in the pump is just not holding well. It's not an issue. Just crank it before the pump stops, you'll get the timing down after a few tries.
I don't think it's as big of an issue as some as long as running fuel pressure is correct.

Running bad when cold could be a coolant or intake temp sensor. They are cheap enough, and the truck is old. Probably just buy new ones. Remember to get the 2 wire coolant sensor, the single wire sensor is for the gauge.
When was last plugs wires and tuneup.
Does your truck happen to have mass air. The sensor could be dirty and cause some issues.

 

Thanks for your responses! I have a fuel pressure gauge at home in California, last time I checked it, the pressure went to 10 lbs first time I turned on key, then seemed to climb 5 lbs or so everytime I turned key to 30 PSI. Then I let it sit no running and pressure stayed at 30. But the misfiring has gotten a lot worse in the 3 weeks or so since I tested it. I have replaced 2 ECT sensors, 1 ACT, cleaned the Mass Air Sensor. Plugs, wires, cap rotor 10 months old. Coil 4 months old, TFI is 6 months old. I just put a new Cat on along with 3 O2 sensors, I had an EGR malfunction I kept chasing and killed my old cat towing my race car trailer. I replaced all 8 injectors 6 months ago, with 8 supposedly brand new ones, as this truck has never liked cold temp running since I bought it last November. I will try to find a shop here in San Antonio to check my fuel pressure. If I cant I guess once I am unloaded I will truck on back to California. Also, if the injectors are causing a miss by not activating, then my Cat should be OK, I think, cause no unburned fuel will be going downstream. Well, again thanks! Dale

 

That is not good, you should get 38-45psi within a couple primes of the pump and that should also be the pressure you see with the engine idling and vacuum removed from the fuel pressure regulator(with vaccum on the regulator you should see 32-35psi and it should always rise when the throttle is opened..never drop). So there is a good chance you have a weak pump, check valve problems if this is a dual tank truck, clogged fuel filter, or one or more leaking injectors.

 

Thanks Paul!

 

I went to a NAPA auto repair shop and spoke with the techs there about the problems with my truck. They said they wanted to check the fuel pressure and did. It was 30 psi idling, and when shut off for 20 minutes it stayed there. So I asked them to change the fuel filter, and I would try running it a bit. So they did, and I did. It seemed better, so I put some Sta-bil fuel treatment in each tank and filled up with fuel and got on I-10 and headed West. It has ran pretty good, I have gone 300 miles, and it only made one little hiccup within the first 30 minutes. So I am at a motel for the night, we will see what the Morning brings!! Thanks everyone! Dale

 

Here's the update. Truck malfunctioned badly in West Texas, on I-40, Fort Stockton to be exact. I went to the local Ford dealer, the service manager lady was nice, but said they could not look at my truck for several weeks! She gave my a list of 3 shops that handle work they can't or don't want to work on. First shop was not open, but looked like a wrecking yard, 2nd shop looked more promising, only 2 trucks in shop, waited patiently till owner off the phone, and went over my problem, he said, he was snowed and I could leave it, might get to it in a month! I found a NAPA store and tinkered with truck in their parking lot. Fixed a poor ground, and said lot's of prayers. Got on I-40 and made it to Los Lunas, NM with lots of intermittent misfiring. Spent the night, got up in AM, same thing, ran like crap until warmed up, got back on I-25 to I-40, broke down in Mesita, NM. I sat there for a while, and pulled out my spare distributor from behind back seat, and replaced it by the side of Interstate. Timed it by ear, with timing spout out, and it ran great! That damned distributor had just been installed by previous owner less than a year ago! Now back in California, will time it with light later! Never going on another trip without a spare distributor. Thanks for responses and suggestions! KEEP ON TRUCKIN!! Dale