New to this site. This is the most informative site I've found on the 6.5. When I start the truck up, sometimes it will shut off when starting to back up. Then it's difficult to start but eventually crankls after about three tries and turning it over quite a bit. I don't think this could be the PMD as it was just recently replaced with a FSD/PMD cooler. Also, I'm pondering relocating the PMD/FSD outside the engine bay. I like Quantum Mechanic's (I think that's the person) idea of placing the PMD in an airfliter behind the grill. What up there has to be removed to get it in that position?

I bought this truck with 64,000 miles on it. It was practically brand new and in perfect condition. At about 90,000 (current), I've had nothing but problems which all seemed to really start when I ran it out of fuel one time. What kind of problems could be caused by making this bonehead mistake (air in the lines or something)? It started stalling, sputtering and cutting off after this point. Took it to a dealership and they installed the FSD/PMD cooler.

I'm definitely not a diesel mechanic and any help would be greatly appreciated. Around here, 6.5 specialists are few and far between.

Thanks

How long ago did you run it out of fuel? I have heard of people replacing injectors and starting up without burping the lines so I'm not sure how much air would have to be in the lines to cause you problems. I hope for your sake it is just air in the lines. You say it starts then stalls then cranks for an extended period before starting again, but then what, does it keep running with no further issues. Since you have stalling prob's with a new FSD, I would say some other good parts to look at are the lift pump and the OPS switch. Good luck.

It's time to trouble shoot the fuel supply system. Does the lift pump come on if you jump the orange wire to the grey wire on the LP relay on firewall (under the fuse link plastic cover). When you bleed the system or drain the water it helps to power the LP.

At idle if you open the air bleed on top of the filter does fuel come out or does the engine die? How old is the air/fuel filter?

Do you drain the brass T that comes off the filter housing to remove the gunk in the bottom? it will build up otherwise and cause a restriction to flow.

PMD will make it stall but the air or low pressure in the fuel system can also do it.

I've had nothing but problems which all seemed to really start when I ran it out of fuel one time. It started stalling, sputtering and cutting off after this point.

Took it to a dealership and they installed the FSD/PMD cooler.
Hold the phone, the DEALERSHIP installed a remote FSD cooler for you?????
GM released a tech bulletin about them, they're supposed to be getting rid of them not installing them for people.

Sounds like you have fuel supply problem weak or inop supply pump or OPS, plugged fuel filter or your drawing air somewhere. Open the bleed on top of the filter with the engine running and let us know what happens.

"Then it's difficult to start but eventually crankls after about three tries and turning it over quite a bit."

Please explan this sentice a bit more. Does the truck crank right away or do you have to attempt to engage the starter more than once? Are you attempting to start before the glow plugs are satisfied which would account for prolonged cranking time.

If the truck only fails when you are backing up and will not engage the starter right after that I would look for an electrical connection that is opened because of that motion. First remove the grounds form the battery and check the large nut on the starter for tightness. This nut is a conmmon fault on none starting.

If the truck fails when backing up but will engage the starter right away not start the engine I would look for an open electrical connection in the fuel pump circuit. make a temperary connection to the hot wire on the fuel pump and bring it into the cab. When the failure happens turn the key to the on position, 94 trucks should supply voltage to the fuel pump in the on postion, and check for voltage.

'94s don't supply voltage when "on" only when cranking and then after oil pressure is established.

Texas Diesel Guy,

The FSD cooler is the one that sits on top of the intake, not remotely mounted. I may have caused confusion there. The dealership seemed to be doing me a favor as I was prepared to have the injection pump replaced, thinking that must be why it was stalling, etc. The mechanic there told the pump was fine and it was the PMD. The OP switch must have been replaced too because about a day after bringing it home it would not start at all one morning. Got it back to the dealership and they called a day later, stating the truck was ready to be picked up. I never asked what they fixed. I was just satisfied to get the thing back.

Before all this happened, I had driven this truck on two 23-hour, nonstop round trips with absolutely no problems. Now, I'm afraid to leave my driveway. I'm sick and tired of all the Ford people around me telling me to go get a Ford. Nevermind, they've spent thousands repairing the Fords. From what I understand, Ford doesn't even make the motor. I've been told International does.

Anyway, I'm going to look at everything that's been mentioned here to the extent of my mechanical ability and try to figure out what the problem. I'll post a response when I've figured it out.

Thanks for everyone's responses. This is definitely the most informative site I've found. Another site I went to seemed to suggest that every problem on a 6.5 was caused by the PMD.

Howie,

A little more on the starting problem. It will crank fine initially (after glow plug light goes off of course). When you start to back and even upon stopping when backing up, it will cut off. After that, it is hard to crank. This tends to happen after the truck has run for a while and then been parked. Example: 40 mile trip. Stop to eat. Get back in truck. Crank it. At this point when you back up, it will sometimes stall. I'm miffed.

[QOUTE=11m]Thanks for everyone's responses. This is definitely the most informative site I've found. Another site I went to seemed to suggest that every problem on a 6.5 was caused by the PMD.[/QUOTE]
That smells like A-1.

Where do you live 11m?
Perhaphs someone here can help.

which smells like ASS

Texas Diesel Guy,
The FSD cooler is the one that sits on top of the intake, not remotely mounted.I call that a remote mount in my book.
Sounds to me like you maybe really did need a pump and they were trying to do you a favor.

That is remote... just not remote enough. Why pull it out of the fire if all your gonna do is cook it on a little pan above the fire. Get an extension harness like this one or cut/solder splice the factory one to get that thing out of the engine bay. http://www.kennedydiesel.com/detail.cfm?ID=134

It was the lift pump. Started opening the air bleed on the filter housing and no fuel was coming out. About two turns into it, she died. Ordered one today. Thanks for all the help. Without this site, where would one be? My guess is on the side of the road. Murphy's Law is my new mantra when dealing with this thing. What's so sad is that this truck is eye candy, exterior and interior.

Thanks again men.

Are you sure it was lift pump, and not the OPS? Or, maybe a combo of both. Hate to see you put on new pump to find it was OPS.

Pull the plug on the lift pump and run a long wire to it on power side and local ground; and see if direct power via battery, fuse/toggle switch for slave test to the pump is feeds/delivers correctly, do a bucket test off the drain volume vs time.

Lift pump is a 15 gph pump which works out to 1/2 pint in 15 seconds of pump run or .24 liter in 15 seconds per GM manual minimum of 3 psi/21kPa

Unfortunately, I read these post too late. Installed the new lift pump and still no fuel coming out of when opening air bleeder. Truck will run but sometimes cuts off at idle. If you push the throttle down for a while and then let it idle it stays cranked. You can also crank the truck with the air bleeder completely off the filter. When you start to screw it back it to almost completly closed the truck will sometimes cut off. With the bleeder out, fuel will come out of the hole where the bleeder was.

I checked all the lines going into the filter. None are clogged. I did notice that there are two electrical connections on the bottom of the filter cannister. What are they for? Do they go bad?

My question - is this the OP switch that has likely gone bad? How is it related to the lift pump? I thought if the OP switch was bad the truck would not crank at all. Should I just get another OP switch?

Once again, I appreciate any advice.

Thanks

OP switch (Oil pressure switch). It gives the signal for oil pressure and make the lift pump come on. Some believe that the OPS cuts the lift pump to kill the engine. Actually, it cuts the pump in case of an accident. Loss of oil pressure during an accident kills the lift pump so fuel doesn't go pumping everywhere. The engine can continue run with out the lift pump running, just not at it's best.

Is fuel coming out under pressure, or just drizzling out?

It just flows out of the top with no real pressure. When you crank it up with the bleed in and start unscrewing the bleed, nothing comes out. So from what I'm understanding the truck can still run without the OPS working but the lift pump will not work if the OPS doesn't work? Is that correct.

Something else I noticed lately. The oil pressure gauge used to always stay "straight up" at 40 PSI at any RPM. Now, it flucuates to about 60 PSI at 2000 RPM and drops well below 40 PSI at idle.

On the '94s like ours the lift pump is powered directly during cranking so if you get fuel to come out while your cranking that means your lift pump is okay. After it starts and oil pressure is established the OPS sends power to the pump. If the truck dies and does not push fuel out of the air bleeder when running the OPS is probably bad.
Easiest and safest way to bleed off air on these pre ODBII trucks is to leave truck off with the bleed screw loose but not removed. Then apply 12 volts to terminal "G" at the ALDL harness under the dash by the drivers left knee. Its the bottom left terminal. This will power the lift pump and purge the air out of the filter housing, when you get a stream of fuel shut the bleeder and remove the jumper.

Lupey,

What your saying is that the OPS is probably dead, right?. So replace it and use aforementioned method to bleed air out of fuel system. I think I'm going to move forward with replacing the OPS regardless. Basically, I have a new lift pump and OPS and maybe even piece of mind (at least for a couple of days).

Thanks for the help and advice on bleeding air out.

Lupey, why not just jumper the lift pump relay on the firewall. That's what I do when I change the fuel filter. In fact, my brother has installed a little switch mounted on the firewall for just this purpose. This way he doesn't have to jumper it each time, he just throws the switch and presto, lift pump comes on.

Just another idea...

-John



Easiest and safest way to bleed off air on these pre ODBII trucks is to leave truck off with the bleed screw loose but not removed. Then apply 12 volts to terminal "G" at the ALDL harness under the dash by the drivers left knee. Its the bottom left terminal. This will power the lift pump and purge the air out of the filter housing, when you get a stream of fuel shut the bleeder and remove the jumper.

Pull the fuse, attached right next to the relay, and jumper there - don't have to break any wire insulation.

Plug one end of the fuse into the socket, connect +12v to the other end of the fuse.

Drivetrain reacts to torque in opposite direction when in Reverse - symptom is indicative of loose\frayed\bad connectioin in harness, including Grounding.

Lupey, why not just jumper the lift pump relay on the firewall. That's what I do when I change the fuel filter. In fact, my brother has installed a little switch mounted on the firewall for just this purpose. This way he doesn't have to jumper it each time, he just throws the switch and presto, lift pump comes on.

Just another idea...

-John
This works on all 6.5L's with a 12v pump. I use the relay I added to carry the LP's electrical load, easiest by far to jump.
On a stock truck I'd jump the fuel pump relay('94's different from '95-'00).

But a switch sounds nice. chevy94-6.5 iirc has one in cab to prime the fuel system if he stalls in traffic without popping the hood or stopping for that matter.

The best system for OBDI trucks IMHO, wire the lift pump to a circuit on the fuse panel that is HOT with the Key ON. Can't go wrong, and you'll hear the pump every time you get in the truck and know its working. Primes the supply system and the IP.

All you need is one hot wire (verify hot with Key ON only), connect it to the colored wire on the supply pump and leave the ground wire like it is.

I replaced the lift pump and the oil pressure switch and finally all seemed back to normal with fuel coming out of the air bleed on the filter just like the old days.

Made a short trip of about 25 miles. The SES light would come on for just about five seconds and then go off. This happened four times on the round drip of 50 miles. The truck ran fine otherwise. No stumbling, hesitation, missing, etc.

Got home and tried the paper clip method for code reading. The only code with the SES flashing light was 78. Is anyone familiar with this.

Thanks

DTC 78 is WG Solenoid failure. I keep getting the one too but haven't figured out why yet.

78 is over/underboost. Check to see if you have any vacuum leaks, poor vacuum. Vacuum pump should be providing ~20" vacuum. The WG 'noid can either stick, and you may get overboost under hard acceleration. Make sure that your actuator arm is free moving while the engine off too. With engine at idle check to see that the actuator arm is strongly pulled in, and almost unable to move by hand. Most common failure is the silinoid itself, it may work sometimes, or not at all.

My book listed it as "failure" instead of over/underboost I thought. Oh course I'm at work so will have to look up later. I thought Over and Under boost had their own codes? My WG noid is new and working so I'm still waiting for down time to T/S mine.

I think I found my problem. The little black hollow line that goes from the actuator (guessing here) over to the back of the driver side valve colver was out of the hole it goes in. This is a plug with a white line and a black line which then plugs into an electrical unit. I assume this is a vacuum line. Basicallly, the vacuum line was unplugged. This may have happened as I was climbing around in there when replacing the oil pressure switch which was a joy.

Where do you guys get these code books? Seems to be a "hot" item for 6.5 owners.

Has anyone ever attempted to overide all the electrical stuff on these trucks and just make it more along the lines of a race car (oval track) as far as battery to switch to starter/glow plugs, etc. Basically - a noncomputer controlled 6.5.

Thanks

Buy a 6.5L manual and it will have the codes, but there listed in the faq area.

Has anyone ever attempted to overide all the electrical stuff on these trucks and just make it more along the lines of a race car (oval track) as far as battery to switch to starter/glow plugs, etc. Basically - a noncomputer controlled 6.5.

Thanks

You could buy a '92 or '93 model. They dont have any of the 'electircal stuff' ( even have mech fuel pumps) but they aren't as fun to play around with! (some here may not find 'fun' the correct word;)) They also dont seem to get as good fuel economy. My brother has a '92 with the same gears and no Crewcab/dually and gets worse mileage than I. Also, the computer does provide other advantages as it attempts to prevent damaging the engine when sensors detect certain conditions. Its my opinion that what is best is to get to know and understand the system and work with it rather than remove the electronics.

But to answer your question directly, you can defeat some of the electronic controls such as the boost control, vac pump, waste gate, OPS, ect. Just keep reading on this website. There are bunch of guys that know the 6.5 better than the GM engineers ever did.

-john

This saga never ends. Took the truck out today and it ran fine for about five miles. Then it missed hard one time and went into the so-called limp mode. Returned home and checked codes. Got 17, 18, 35 and 78. What in the *#&^ is going on man? I about done with this BS.

17 - Hi Res Circuit Fault
18 - Pump Cam Reference Pulse (Lo Res) error
35 - CTime too Short
78 - Boost sensor out of range

So thats both pickups in the optic sensor, Fuel Solenoid problem and you said you think you found the problem with your boost/wastegate system right?

17 and 35 are some times tripped by air in the system...but from your description of a 'hard' miss I think its an electrical problem somewhere.

Clear the codes and see what your Closure Time, DES/ACT timing, CAM/Crank Miss Counts read.

11m,

I understand your fustration, I had a similar experience a year ago with my truck. It kept giving a wastegate code, the crank postion sensor code and going into limp mode. After 2 sensors, 3 wastegate selnoids and having PMD hickups I gave up and took it to the stealer and it was an electrical problem, $60 and all I think they did was unhook the pcm and plug it in but it fixed the code throughing problem. A month later they replaced the PMD.

I later found this site and I have learned a lot from these guys!!!! Not saying for sure you are having the same issues as I had but it sure sounds like it. It"s like some of the other posts, these trucks are finiky when it comes to the electronics.