7.3 dies at stops at times

[Fordracer]

I'm at my witts end on this one. If you drive it first thing in the morning it will die at the same stop, 4.5 miles, every time. After that it might die when ever it feels like it or it might not but the next morning it will do it all over again at 4.5 miles. I've driven it over 100 miles trying to figure this one out and now it will die at 2 miles. It seems to die more when your foot is on the brake or turning the steering wheel. I can come to a stop when it is still running and then I turn the steering wheel and it will die some times. This truck has 93,000 miles on it and it runs great and never dies under power just at idle.

Codes p0344 and 340 come up at times. Also sometimes a p0107 will show up.

Recordings show the idle drops slowly when it dies and the IPR nad ICP ramp up as it's dieing. There are no warning lights coming on or gauge fluctuations when it's dieing. ICP koeo is .21 volts, at idle ICP is 475 psi and IPR is 11%, VSS is not spiking. I unplug the ICP and it wont die.

I've load tested the CMP and ICP circuits and PCM ground and power ciruits. Fuel pressure is 60 psi when it dies. I replaced the batteries because one was dead. I've replaced (with known good parts) the ICP, IPR, PCM, CMP, ICP connnector, PCM and IDS relays. I even drove it with the EBP unhooked. Nothing helps except unhooking the ICP connector. The hotline thinks all that's left is to replace the harness if they are available.

Any help or questions would be greatly appreciated.

Thanks, Keith.

[Bruce Amacker]

I sure wish people would tell us what year the truck is when they post a help request. There is a considerable difference in how the Gen 1 7.3 works compared to the Gen 2 7.3.

 

[Fordracer]

Sorry Bruce. 2001.

[Bruce Amacker]

This is one to put a breakout box on and start check basic electricity to the PCM. Powers and grounds, voltage drops on all of these, ACV output from the alternator, dirty power, etc. You might want to try driving it with the alt unplugged. The baro is internal to the PCM so if a 107 sets with different PCMs the PCM is telling you it's pissed off about power somewhere. The 340/344 will set if it's cranked for a while in a no-start situation, but you didn't tell us if it starts right back up or cranks a while to start. I'm a scope dude so this is where I'd start, it only takes an hour to do this.

 

I did have a 7.3 years ago that had a bad harness and bled power from the turn signal circuit to the CMP circuit. I didn't change the harness, I only put a piece of polyloom over the green wire to isolate it, which fixed the problem. On yours I would suspect the CMP signal might be corrupt, or wrong CMP air gap, or perhaps cam end play on a long shot. Adding some CMP shims might be a backyard test.

 

Unplugging the ICP puts it in default, raising the IPR command and ICP to cover up the problem, which may not be in the HP circuit at all.

 

Where did you check the FP at? Fuel sample from the drain looks good? Is this your own truck? Is it Cal emissions with a GP module? I'm assuming it's an F-model?

 

[Fordracer]

The alternator is putting out .055 acv. I'm topping off the batteries now before I drive it with the alt unhooked.

 

I've only used a scope a couple times in my career but would like to learn to use it more. What ciruit should I test on the CMP? Should I check it at the PCM connector or at the sensor?

 

When it dies it will start back up within a normal cranking time but will die right after it starts and it will do this for 3-5 times before it will stay running. Will a 7.3 set cam sensor codes like a 6.0 will when it dies? I was checking the cam sensor and circuits at first untill the hotline says they will set the codes when they die and to ignore it.

 

I checked the fuel pressure at the front of the right head. The fuel is clean but has a brown tint to it instead of green.

 

This is a customers truck (F-250) and not a California emission one.

 

Thanks for your help Bruce.

[Fordracer]

I just finished driving it 6 miles with the alternator unhooked and it didn't die. I'll recharge the batteries again in the morning and drive it again. When I unhooked the altenator I noticed the plastic insulator between the wire and the altenator was cracked if that means anything.

[Bruce Amacker]

The alternator is putting out .055 acv.

 

That's a good number.

 

I'm topping off the batteries now before I drive it with the alt unhooked.

 

Don't "top them off" unless they're low. If the alt is working fine, you're overcharging them, not "topping them off". The truck should run several hours at least without an alt.

 

 

I've only used a scope a couple times in my career but would like to learn to use it more. What circuit should I test on the CMP?

 

CMP signal is pin 21 at the PCM. Use a BOB if you can.

 

 

Should I check it at the PCM connector or at the sensor?

 

The signal should be the same at both ends of the wire.

 

 

When it dies it will start back up within a normal cranking time but will die right after it starts and it will do this for 3-5 times before it will stay running. Will a 7.3 set cam sensor codes like a 6.0 will when it dies?

 

 

Yes.

 

I was checking the cam sensor and circuits at first until the hotline says they will set the codes when they die and to ignore it.

 

I checked the fuel pressure at the front of the right head. The fuel is clean but has a brown tint to it instead of green.

 

Try putting some Stanadyne Performance Formula or FMC lubricity additive in it and see if it runs different. Brown doesn't sound good.

This is a customers truck (F-250) and not a California emission one.

 

Thanks for your help Bruce.

CMP pin 21 idling:

 

[Fordracer]

I didn't realize the batteries would last that long. I thought I would be lucky to make it 6 miles. So far I've driven it 18 miles no noticable battery drain.

 

I hooked up the BOB and did a voltage drop on the powers and grounds. The grounds were .036 - .039 and the powers were .073 - .081.

 

I scoped pin 21 with the alternator unhooked and hooked up and both ways they look just like the patern you showed.

 

I drove it yesterday afternoon and it didn't die but it doesn't always die in the afternoon. I just finished driving this morning when it will always dies and it didn't die. I'll try again tomorrow morning with the alt unhooked and if it doesn't die I'll hook it back up and try it again the next morning and see what happens.

[Bruce Amacker]

I didn't realize the batteries would last that long. I thought I would be lucky to make it 6 miles. So far I've driven it 18 miles no noticeable battery drain.

 

 

There's a formula you can use to determine how far you can drive- take the reserve capacity of the battery (measured in minutes) or amp hours divided by the draw. The 7.3 calls for a battery with a RC of 150 minutes and an amp hour rating of 90. Being that the truck has two batteries and guessing that the PCM draws roughly 25 amps without the A/C and accessories on, you should be able to drive 300 minutes (5 hours) using the RC calculation or 7.2 hours using the amp hour method. Either way, it's a long damn time. When I was a kid I had a car and drove it (occasionally) for years without a charging system. A buddy of mine had a Fiat and his alternator never worked for years, either, and that was a daily driver. These cars saw plenty of used battery swaps and battery chargers to stay on the road.*

 

 

 

I hooked up the BOB and did a voltage drop on the powers and grounds. The grounds were .036 - .039 and the powers were .073 - .081.

 

I scoped pin 21 with the alternator unhooked and hooked up and both ways they look just like the pattern you showed.

 

I drove it yesterday afternoon and it didn't die but it doesn't always die in the afternoon. I just finished driving this morning when it will always dies and it didn't die. I'll try again tomorrow morning with the alt unhooked and if it doesn't die I'll hook it back up and try it again the next morning and see what happens.

 

 

Try some Stanadyne.

 

 

 

*Reserve Capacity is the amount of time a battery can last driving after the alternator has failed.

*Battery Council International defines this as” the number of minutes a new, fully charged battery can be discharged at 25 amps and still maintain a voltage equal to or higher than 10.5 volts for a 12 volt battery.”

[Fordracer]

I drove it this morning with the alternator unhooked and it died 4 times and it would start right back up again. The first time it died was at a stop light and I turned the steering wheel back and forth and then it died. The other times I was coasting or stopped. When I got back to the shop the idle would drop to almost 0 and then jump back up to idle rpm and it did this probably 3 times. Also the check engine light was on while it was doing this and then it went off after it starting running normal. I had a P0344 in it again.

 

Something I forgot to mention earlier, I was running the KOER self test and right when the test ended it died and would keep dieng after I started it 4 - 5 times before it would stay running. I've ran the test since then and it won't act up.

 

 

The truck is about out of fuel so I need to put 5 gallons in it. Should I put the Stanadyne in the tank or the filter housing?

 

Do you think I should scope the cam sensor circuit while driving and see what it does when it dies?

 

Thanks for all the help Bruce.

[Bruce Amacker]

I drove it this morning with the alternator unhooked and it died 4 times and it would start right back up again. The first time it died was at a stop light and I turned the steering wheel back and forth and then it died. The other times I was coasting or stopped. When I got back to the shop the idle would drop to almost 0 and then jump back up to idle rpm and it did this probably 3 times. Also the check engine light was on while it was doing this and then it went off after it starting running normal. I had a P0344 in it again.

 

Something I forgot to mention earlier, I was running the KOER self test and right when the test ended it died and would keep dieng after I started it 4 - 5 times before it would stay running. I've ran the test since then and it won't act up.

 

 

The truck is about out of fuel so I need to put 5 gallons in it. Should I put the Stanadyne in the tank or the filter housing?

 

I'd put two bottles in the fuel tank with 5 gallons and see if it runs better.

Do you think I should scope the cam sensor circuit while driving and see what it does when it dies?

 

Thanks for all the help Bruce.

Yow, tough one. If you can scope the CMP while driving I don't think it would be time wasted. See if you can monitor your MFDES and FPW just before stalling. FPW- Fuel Pulse Width- usually 1.5-2.5 idling.

 

 

I'm not going to rule out injectors on this one.

 

Good Luck!

 

[Fordracer]

This is what I have on the recordings I have of it dieing.

 

RPM 650 581 499 396 283 108 76

 

FPW 3.15ms 3.04 4.13 4.92 4.97 4.97 600us

 

MFDES .18gr .18 .38 .51 .76 1.10 0

[Bruce Amacker]

PW is off the map, making me look harder at the injectors. Did you check FP at both heads? Try a LOT of Stanadyne and see if it runs better. Do you have a history on the injectors, have they been changed?

 

[Fordracer]

I already told the parts department to get me 2 16 oz. bottles but now I told them to get the 64 oz. one. How much should I put in with the 5 gallons of fuel I'm going to put in. There might be 2-3 gallons left in the tank now so that would be around 8 gallons total.

 

He's been a regular customer of ours. He changes his oil every 5,000 miles and no injectors that we know of. He traded the truck in yesterday on a 2008 F-150. He's been real patient with us but he sold his camper a couple years ago and only uses this truck to drive to work so he doesn't need it anymore and his wife has been on him to get rid of it for quite a while. So now it belongs to us.

[Bruce Amacker]

A lot is a very generic term. I usually drain the FF housing and fill it with Stanadyne and see if it runs better. This is against all mfr recommendations, but if I were working on the truck I'd put at least a couple of bottles in the tank and see how it ran. If it runs better, either the fuel is bad or the injectors are bad.

 

Good Luck!

 

[Fordracer]

I drove it thursday with no problem but when I drove it this morning it died and seems to be getting worse. It was actually dieing in my stall for a while so I scoped the cmp pin 21 and it didn't show any problems when it died, the pattern got wider as it died. The FPW is now 2.8 at idle and MFDES is .13, Load - 18%, IPR - 12.5%, ICP - 480 lbs at .85 v.

 

While the BOB is hooked up I checked pin 87 for the ICP and koeo was .245 v but the pid always showed .22. I hooked up my test ICP and it read .26 v so I tried a new one and it was .241 v on a warm engine. Now here is were it gets more wierd, I came back from lunch and the engine cooled down and I checked the voltage again and it was .310 v and then I heard the glow plug relay click off and it went down to .234. I tried this a couple more times and every time the glow plug relay is on the voltage at pin 87 goes up to .310 v.

 

Do you think I have a ground problem somewhere?

[Fordracer]

I just tried putting other loads on the battery and watching the ICPv at pin 87 and with blower on position 1 it's .248, 2 - .233, 3 - .222, 4 - .208. The headlights make it go from .248 - .244. The wipers make no difference on the voltage. When I said the voltage was .234 in the last post the blower was in position 2. With blower off or on position 1 it's .248.

[Bruce Amacker]

You have a ground loop of .02v or so which is not to be concerned with, it's common.

 

With your IPW too high (considerably) and your MFDES too high I'm still thinking injectors. Did you try Stanadyne?

 

 

[Fordracer]

Yes. I filled the fuel filter housing and put 32 ozs in the close to empty tank and then put 5 gallons of fuel in tank. I did this on wednesday night and drove it thursday with no problem but today it started acting up again.

[Bruce Amacker]

Did you check FP at both heads?

 

[Fordracer]

I checked it at the right head before. This morning I checked it at the left head and when it died the pressure was 65 psi. It's 55 under load.

 

When it died this morning I noticed the check engine light came on before it died and set P0344 like it always does. Usually it comes on after I restart it.

 

Another thing I tried the last two mornings was when trying to restart it after it dies if I push down on the accel after it starts it will keep on running but die if I let off.

[Bruce Amacker]

If it's setting the 344 as it stalls, try putting some CMP shims in and see if that changes things. Usually the CMP code sets from extended cranking. I'm also thinking of RFI/EMI interference. If you don't want to put an overlay harness in it try isolating the signal wire with small polyloom....

 

[Fordracer]

I put a .010" shim in it and it will fire and die, it won't stay running.

 

Do you mean overlay all three wires?

[Fordracer]

I got to thinking about it not running with a .010" shim. I've never shimmed a sensor before but if .010" was enough to kill it is the sensor to far away without the shim? I have some NOS black sensors at home and I'll bring one in tomorrow and see if it measures deaper than the gray ones and put it in the truck and try it even if they're the same.

[Bruce Amacker]

I put a .010" shim in it and it will fire and die, it won't stay running.

 

Do you mean overlay all three wires?

 

Wow, that's big info, it should run with a .010". They're not the same, IIRC the gray is .020" shorter.

 

Do you have access to a CMP depth gauge?

I'm wondering about cam walk, among a bunch of other things......

 

Yes, I'd overlay all 3.