I'm new to your forum. I'm working on a friend's 1997 F250 HD 4x4 auto long bed with two fuel tanks. It's got the 7.5l/460 cu. in. V8. It's fuel injected but with a distributor. Unable to find a Data Link (16 pin ) connector in passenger compartment, but did find a data connector under the hood on driver side near air filter and hooked up scan tool--no codes, since battery had been disconnected.
Problem: Truck has been sitting for 6 months or so. It was running fine but now it's blowing fuel and possibly water (coolant?) out the tail pipe. Very heavy fuel smell from exhaust. Cat is dripping fuel. Haven't checked compression yet but will be next. Assume it's a blown head gasket Replaced fuel pressure regulator, but no change. Old FPR held vacuum OK. All injectors firing based on stethoscope check. Owner says it couldn't be head gasket. It was running fine last year. No water in engine oil. No oil in radiator coolant. 129k miles.
Last edited by RedWomack; 03-23-2011 at 05:25 PM.
Reason: Spelling error: fiend vs. friend
Thanks for the replies, guys. Forgot to say that the engine starts easily and runs rough--like it's heavily choked--dumping fuel and white smoke out the tail pipe--heavy fuel smell. No leaks in the fuel rails that I can see. So yes it has spark. Owner said he pulled the plugs last year and they were OK--but we will pull them again and do a compression test on all 8 cylinders. Will make sure firing order is correct. Borrowed a Snap on fuel pressure gauge but got no pressure reading through the Schrader valve on the fuel rail. Not sure the core in the valve was depressed enough to allow fuel to pass. Have a new pressure gauge on order and will check again. When I depress the Shrader valve core with a small screwdriver--after shutting off the engine-- only a small spurt of fuel comes out--no major spray. Supposed to have 39 psi or so residual pressure--and maybe 70 psi when fully pressurized. Could there be water in the fuel tanks that would do this? Leaky or stuck open injectors? Will check again to see if there are any damaged fuel lines. They're all steel I think. Clogged fuel filter?
Two main possibilities here, at least one injector is stuck open or the fuel evap system is totally flooded with raw fuel and it's being sucked into the engine.
This evap system has a charcoal canister on the passenger frame rail just behind the rad support so it should be pretty easy to check for the presence of raw fuel, and the canister is connected to the TB via some rubber hoses and in some cases the canister purge valve.
This system becomes flooded if the truck has dual tanks and the check valves in one of the fuel delivery modules gets stuck open which allows the other tank to backfill into it and overfill into the vent system and even out the tank fill tube in some cases.
A stuck injector should also be pretty easy to find, just look for the soaked spark plug. If fuel pressure drops immediately when the engine is killed that's usually a sign of a stuck injector. And a side note, with some pressure gauges you have to remove the schrader valve core from the fuel rail before attaching the gauge or it won't register anything, something that is easily done with a simple tire valve tool.
Conanski, thanks a lot for your input. We took a look at the Evaporative canister and hoses--no obvious problems. Hoses seem in good condition. Canister doesn't seem to be full of fuel. Decided to pull the plugs and check compression. Black soot on 4 of the 8. Compression numbers are: #1-150 psi;#2-135 psi; #3-175 psi; #4-175 psi; #5-180 psi;#6-175 psi; #7-135 psi; and #8-160 psi.1234 are right bank and 5678 are left bank--passenger side/driver side respectively, front to back of engine. Does this mean that the head gaskets are still intact--despite the 40 lb differences for #2 and #7 cyclinders? Don't know what the compression specs should be on this engine. Haven't found them in the Chilton book I have yet. Checked firing order. It's correct: 15426378, counterclockwise distributor rotation. Don't have any scan codes since battery has been disconnected and can't drive it blowing fuel out the exhaust. Will change fuel filter and have decided to install remanufactured GB injectors and new plugs to work back from there--and start rechecking sensors and other fuel injection system components. Owner says one of the two tanks is empty--so will put fresh gasoline in "empty" tank. Truck is outside in driveway and rain has been keeping us from working steadily--here in northern California. Still awaiting anew fuel pressure gauge kit and fuel line disconnect tools. Pulling the injectors doesn't look like too big a job, but I believe they're the originals with 127k miles on truck.
Conanski--Forgot to mention we haven't looked at the check valves on the twin tanks. You said "modules." Are those check valves mounted on the fuel pumps inside the tanks? If one of them is stuck open it sure might explain why there is so much excess fuel in the system. I'll look in the manual again on where the check valve(s) are located. The Chilton manual doesn't cover the 7.5 liter v8 engine. Haven't been able to find a good schematic to show all of the fuel injection system components under the hood.
Guys: Still working on the 97 F250 (7.5l) fuel problem. Was able to check fuel pressure at Shraeder valve again. At first--no reading--zero. Have a new OTC gauge with right fittings. Did KOEO--ignition on, engine not running. Hear fuel pump buzz for both tanks--switching the tank dash switch--so both pumps seem to be working OK--although forward tank is on empty and rear tank at about 1/4.. Truck has always started but run rough, blowing fuel out exhaust pipes, cat dripping fuel.Truck ran "fine" 6 months ago and has been sitting. Heard clicking, crackling noise in engine compartment. Stethoscope on injectors found #1,4,5,6,7 firing intermittently WITHOUT the engine running. This can't be right, right? Went to Power Distribution Box and swapped relays for #2 Fuel Pump and injector clicking stopped with KOEO. Also see that #1 relay is for PCM. Now have about 30 psi fuel pressure. Will spike to 40 psi at start up. Engine starts up and is definitely running a lot better--but still blowing a lot of fuel vapor out exhaust. Before swapping relays, fuel pressure would drop to zero with ignition shut of. Now holds residual with no leak down. Not sure we have found the whole problem, but if the injectors fire KOEO because of faulty relay that would help explain excessive fuel dumping into system. Have new plugs and injectors ready to install also. And have new fuel filter to install. Will fill both tanks to at least half way. Wondering if the CAT and muffler could be full of liquid fuel? Also convinced owner the engine oil was at least 2 to 3 quarts overfilled--and drained back to correct level.
Sounds like you have bigger problems than me, I've got the same truck except 2wd. I'm looking for a vacuum diagram to make sure their connected correctly, did head job and some broke during removal. Was wondering if you could help me out with a photo of that motor or tell me the routes. The areas I need are Vacuum Reservoir @ Passenger fender, Map @ firewall and Vacuum Tree @ intake manifold, it's got 5 outlets but I can't remember if it had 2 or 3 lines going to it. Any help would be great, Thanks.
Yes, I found some vacuum diagrams on the Mitchell1 DIY/SnapOn website for this 7.5 liter engine. The Chilton manual I have doesn't cover this engine. There are two engine bay drawings of components in the engine bay and also a couple of vacuum diagrams. I was having trouble identifying all the different stuff under the hood and didn't have any pictures--which reminds me--I will take some pics and try to post them next week. I'm going to try to attach the vacuum diagrams to this thread. It will take me a little while. I decided to invest in the Mitchell 1 site for one year ($30) per vehicle. One week is about $12.50 per vehicle. They've got a lot of good data there. How's the weather in southern California? It has been raining for days up here--San Francisco Bay area-- and we're tired of it.
(Do it Yourself Automobile Repair Manuals - Mitchell 1 DIY
Last edited by RedWomack; 03-26-2011 at 06:36 PM.
Reason: Wrong word
Yeah Buddy, thanks alot for the help. I've been on the search for awhile and it gets more confusing each book I look at. I bought the Alldata online and thier drawings don't match whats under my hood in some areas. I wish I could say it's 80 degrees and sunny down here but it's not, cloudy and sucky is more like it.
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