7.3 IDI won't stay running

[sam shelly]

Hello I'm having trouble figuring out why my truck won't stay running. It's a 93 f250 with the 7.3 IDI. One day I was driving and the fuel filter light came on and the truck stalled shortly after. It would start back up easily but only for a second then stalled again and again and had to have it towed. Only way to keep it running was to hold the pedal to the floor and the RPM still so low it wanted to stall.

So far I've replaced the fuel filter and and replaced the manual lift pump with an electric facet pump. I have a clear line running from the fuel pump to the filter housing and another clear line from the IP return to the injectors. Both lines appear to be full of fuel and not seeing any air but still having issues. Now the truck will idle longer but very rough and will stall after giving it throttle. Sometimes it still dies shortly after startup at idle, it's pretty random.

If I give it throttle the RPMs go up briefly then fall back down/surge and stall. I'm not very familiar with this engine and haven't been able to find this exact issue online, so was wondering if anyone has any ideas. Was thinking replacing the injectors or injector pump next but I'm really not sure

 

[MtnHaul]

Is the injector pump old/lot of miles?

 

[sam shelly]

I don't know how old it is, I've only owned the truck about a month and driven about 200 miles. The truck has about 200,000 miles. Pump looks like it could be pretty old

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[Big Bart]

Some thoughts

Like MtnHaul, it think it could very well be the IP pump. I have seen many a IDI parked or for sale that died or acted up before it would not run or run well, just to be told the IP is bad.

Due to the fact its a little pricey to rebuild one and your fuel filter light came on (Generally tripped by water but sometimes by air.) let's check a couple of things first.

1) Did you fill your fuel filter with diesel before you put it back on? (If not you still may have air in the system between the filter and the injectors.) If you turn on the electric fuel pump and push in the shrader valve you should be able to remove most of the air perhaps still in it. Or you can pull the filter, fill it, and put it back on.
2) Have you tested your electric lift pump to insure it has pressure and flow? Perhaps you had a clog between the tank and the mechanical lift pump. Perhaps your electric fuel pump was bad out of the box.
3) Did you try bleeding the injectors after putting on the filter and clear lines? I would bleed/re-bleed the injectors to see if that helps. In case you have not done so before. Unscrew each injector line say half way and make sure you can lift the line a little. Turn the truck over till each one is spitting diesel. Then tighten them all up (Tight but do not crush the fitting being the Hulk.) and wipe away any excess diesel.
4) You said you installed clear lines. Are you looking at the lines when it is running or are you inside the cab turning the key and feathering the pedal? You want to watch to see if there are air bubbles if fluid is actually moving through the line when starting and running. So if you do not have the wife or mini-me around to help turn the key. Maybe it would help to pick up a remote starter switch. Jump between the positive battery post and the little start post on the starter solenoid. The clear line off from the lift pump is just what is going into the filter. The clear return line is just what the injector did not use. But air can be trapped in the filter, line to IP, the IP, and the injector lines till it has run for a little bit.
5) Sometimes the solenoid on the top of the IP pump goes bad. Working it allows fuel to run into the IP pump so the truck will run. When power is removed (You turn the ignition key to off) it stops the flow and turns the truck off. Make sure the electrical connection is clean, is getting 12v positive with the key on, as I recall you can hear it or feel it clicking on when it gets power. I would turn it on and off say 6 times to make sure all 6 times you feel/hear it activate.

But if you have +100,000mi on your lift pump and everything else checks out, then likely that is what it is. It is a maintenance item but once rebuilt will take you a long ways.

Let's see what others chime in with for other things to check.

Take a couple of pics to share and let us know what you find out!

 

[Big Bart]

Just saw you pic posted so a couple more thoughts.

1) Yes looks like its been in there for some time. The red on the back of the IP would suggest it was rebuilt once some time ago.
2) Looks like you may have a injector line or IP leak. See how everything is wet with oil (Guessing diesel) in a 10" circumference on the back of the injector pump. Back of pump, engine underneath, injector lines, and the give away is the air cleaner. (Unless oily all the way around.) I would also see if any of those lines on the back of the IP are loose. Sometimes they vibrate a loose.
3) Per above, that orange wire is very suspect. It is not factory, if that is not getting 12V all the time or is making a bad connection it could very well be causing your issue.
a) Should be coming out the wiring loom right next to the IP like the white and red one on the side of the IP does.(That white and red powers the cold start advance.) Yet the orange wire appears to head to the firewall or somewhere else. That is not stock so someone wired that in. Could be the issue or part of your issue. (Maybe not.)
b) I would put on a new connector on the orange wire at the IP to just take that connection out of the equation.

 

[gandalf]

These are all good ideas. There are many possibilities why you're having problems. I'll hit another, perhaps a bit less likely, but certainly a possibility.

You say you installed a Facet electric fuel pump. Tell us more about that installation. Lets assume that the Facet pump works as advertised. How did you handle the plumbing? Where did you place the new fuel pump? Did you use the existing fuel line? That is to say, do you have the fuel still flowing through the stock lift pump, or did you install new fuel line from the fuel selector valve to the Facet pump and onward to the fuel filter? IF you have the fuel still flowing through the stock lift pump, check the engine oil level. That's right, check the engine oil level, right away. The stock lift pump has a rubber gasket separating the fuel flow from the oil galley. If that gasket is torn, some of the fuel you're pumping is going through that gasket and mixing with the oil. One outcome of that is that the engine is not getting enough fuel. This doesn't happen too terribly often, but it does happen, and I'd suggest ruling out the possibility.

 

[sam shelly]

The fuel filter light actually hasn't come back on since replacing the filter and adding the electric pump. When I replaced the filter I filled it with diesel kleen and bled the air through the shrader valve. Looked at the lines while my friend started the engine and didn't see any bubbles. I assumed since it starts up instantly that there's no air in the injectors but I'll try bleeding them tonight and check fuel pressure again.

Thank you for the suggestions. I'll work through them and let you know

 

[sam shelly]

Just saw you pic posted so a couple more thoughts.

1) Yes looks like its been in there for some time. The red on the back of the IP would suggest it was rebuilt once some time ago.
2) Looks like you may have a injector line or IP leak. See how everything is wet with oil (Guessing diesel) in a 10" circumference on the back of the injector pump. Back of pump, engine underneath, injector lines, and the give away is the air cleaner. (Unless oily all the way around.) I would also see if any of those lines on the back of the IP are loose. Sometimes they vibrate a loose.
3) Per above, that orange wire is very suspect. It is not factory, if that is not getting 12V all the time or is making a bad connection it could verywell be causing your issue.
a) Should be coming out the wiring loom right next to the IP like the white and red one on the side of the IP does.(That white and red powers the cold start advance.) Yet the orange wire appears to head to the firewall or somewhere else. That is not stock so someone wired that in. Could be the issue or part of your issue. (Maybe not.)
b) I would put on a new connector on the orange wire at the IP to just take that connection out of the equation.

That wire is the key on for the electric fuel pump and goes to a relay. It's connected to the bolt with a ring terminal. I believe the wetness is diesel that shot out of the shrader valve that I failed to clean up all the way

These are all good ideas. There are many possibilities why you're having problems. I'll hit another, perhaps a bit less likely, but certainly a possibility.

You say you installed a Facet electric fuel pump. Tell us more about that installation. Lets assume that the Facet pump works as advertised. How did you handle the plumbing? Where did you place the new fuel pump? Did you use the existing fuel line? That is to say, do you have the fuel still flowing through the stock lift pump, or did you install new fuel line from the fuel selector valve to the Facet pump and onward to the fuel filter? IF you have the fuel still flowing through the stock lift pump, check the engine oil level. That's right, check the engine oil level, right away. The stock lift pump has a rubber gasket separating the fuel flow from the oil galley. If that gasket is torn, some of the fuel you're pumping is going through that gasket and mixing with the oil. One outcome of that is that the engine is not getting enough fuel. This doesn't happen too terribly often, but it does happen, and I'd suggest ruling out the possibility.

So the facet pump gets fuel from a hose connected to the metal line that goes to towards the tanks and the outlet goes up to the fuel filter. I mounted it to the side of the alternator bracket. The mechanical pump has been removed and replaced with a block off plate. Oil level is normal too. Here is a picture of the setup. Ignore the messy wiring I will clean it up once I track down this issue...

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[gandalf]

Reading Brad Barmettler's last post above, he brings up a valid point. That red wire is suspect. It looks too new. It's quite clean. Where is the other end of that red wire? It appears to be headed toward the battery. If it does connect directly to the positive post on the battery, or to a hot positive over on the fender wall, that may indicate a definite problem. It's connection on the IP is hidden in your picture. If it is connected to the front connection point on top of the IP, try disconnecting it, engine off, ignition off. Do you hear a click in the IP? This could be a "temporary" replacement wire to activate the IP. There is all kinds of room for error here. If the wire goes back through the firewall, look for an extra switch somewhere inside the cab.

Some owner fixes are rather ingenious, and rather suspect.

 

[Big Bart]

Ok now you are shedding more light on this topic.

I don't think you truck can run on straight Diesel Kleen. (It's an additive and for lubrication, not intended to replace diesel.) I have never heard of anyone doing this before but my gut says that is not helping your situation. Also would make sense why it is running odd, its trying to burn only Diesel Kleen. I would pull the fuel filter, drain it, put in diesel or ATF. (Non synthetic) Now the trick is you need to run till you get as much diesel clean out of the IP and injector lines as you can. (It will mix with diesel as it goes trough the return lines.) Suggest you bleed at the injectors for a while, but put rags around the injectors to soak up the fuel. Also only crank 10 seconds on, 20 seconds off, to not damage the starter. If you have a 6amp, 10amp, or higher battery charger leave it on while you are doing so.

Maybe I am off base here so lets see if other members have done so without issue. If no one has you need to fix and then move forward. There are still mulitple issues it could be here.

 

[gandalf]

It looks, in your second picture, as though that red wire may power the Facet pump. Is that correct? That is a variation of the way had my facet pump powered. It insures that the pump receives power only when the IP receives power. Good.

There is a slightly heavier red wire running off to the left in your second picture. Tell us about that wire.

You plumbed the Facet in the safest way, eliminating the stock lift pump. Good move.

I'm now off to my daughter's house to help there. I'll be off-line.

 

[sam shelly]

It looks, in your second picture, as though that red wire may power the Facet pump. Is that correct? That is a variation of the way had my facet pump powered. It insures that the pump receives power only when the IP receives power. Good.

There is a slightly heavier red wire running off to the left in your second picture. Tell us about that wire.

You plumbed the Facet in the safest way, eliminating the stock lift pump. Good move.

I'm now off to my daughter's house to help there. I'll be off-line.

Right the red wire from the IP goes to a post on a relay to power the facet pump. The red on the facet pump is connected to another post on that relay. The thicker red wire was there already and is connected to the starter solenoid

 

[Big Bart]

Sam,

I am still unclear of your wiring post and present. To help me understand better please be as clear and concise as possible. Also if you can think of any other things you may have done be sure to list out.

1) The orange wire on top of the IP, where does the other end terminate to? (Can you send a pic.) Did you just put that on this week or was it there when you bought the truck? If already there you need to closely inspect, suggest putting on a new ring connector if that is not what you added this week.
2) Can you take a picture further back of all the orange/red wiring so we can what is going on. It all crosses over and then disapears out of the picture. Get this may all be temporary wiring but would like to understand better how you are wired up.
3) Is the factory wiring for the IP solenoid still connected to the IP? If so does it have 12v positive with the key on? Does the voltage drop dramatically when you go to start it?(Below 9v)

FYI suggest if you have not done so. You put the fan belt back on so when it is running you can keep it running to get the Diesel Kleen out of the injection system.

I still think it could be the Diesel Kleen, so perhaps address that first.

Heading out to work on my son's 67 Galaxie but will check in later to weigh in.

 

[sam shelly]

Sam,

I am still unclear of your wiring post and present. To help me understand better please be as clear and concise as possible. Also if you can think of any other things you may have done be sure to list out.

1) The orange wire on top of the IP, where does the other end terminate to? (Can you send a pic.) Did you just put that on this week or was it there when you bought the truck? If already there you need to closely inspect, suggest putting on a new ring connector if that is not what you added this week.
2) Can you take a picture further back of all the orange/red wiring so we can what is going on. It all crosses over and then disapears out of the picture. Get this may all be temporary wiring but would like to understand better how you are wired up.
3) Is the factory wiring for the IP solenoid still connected to the IP? If so does it have 12v positive with the key on? Does the voltage drop dramatically when you go to start it?(Below 9v)

FYI suggest if you have not done so. You put the fan belt back on so when it is running you can keep it running to get the Diesel Kleen out of the injection system.

I still think it could be the Diesel Kleen, so perhaps address that first.

Heading out to work on my son's 67 Galaxie but will check in later to weigh in.

Sorry I will try to make things more clear. Yes the pump was installed by me this week because I suspected the mechanical pump might be causing the issue. The electric pump made it start easier but engine still stalls.

Attached some pictures of the wiring setup. It's controlled by a 4 pin relay mounted next to the battery. Pin 30 on the relay goes to the positive battery post, pin 86 and the black fuel pump wire are grounded to the chassis, pin 85 goes to the injection pump bolt so it turns on with the key, and pin 87 goes through a 3 amp fuse to the fuel pump red wire.

The factory IP connector appears to be good. There is an audible click from the IP when I connect it with the key on, so I believe that part of the IP is at least working. I don't have a meter to test exact voltage right now but can pick one up after work and test it. I believe the facet fuel pump is working correctly too as I had it going into a bucket earlier and was passing a good amount of fuel. I will have to double check fuel pressure after work, can't remember what it was.

The belt is back on already, that other picture was a couple days old. Will try getting the diesel kleen out of the system. I had seen several posts online to fill the filter with diesel kleen after changing it so that's why I did that.

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[sam shelly]

Fuel pressure off the Schrader valve is 5-6 psi with pump on engine off and about the same at idle. It rises to about 10psi just before it stalls