I have a late 99 f550 with a 7.3. When the engine is cool, it runs like a striped a.. Ape! After about 10 miles at highway speed, it starts slowing for a couple of miles and then just gets progressively worse until it' just barely limping along but surging slightly. I have taken the fuel tank off and found no trash or obstruction ( just had the tank lined a year ago). Also replaced the fuel filter with a motorcraft from the ford dealer. Replaced the inline fuel pump. I don't have the means to check fuel pressure while driving but what it's cold, it was enough to blow out the aftermarket filter o ring and get fuel everywhere. I' m open to the possibility that I got a bad pump that quits when it gets hot? Oh, and I also replaced the PCM or ecm or whatever it' s called this week. I let it idle for about 30 minutes before taking it out today and it still went 10 miles in the fast lane and did the same thing. I'm stumped!!!!!!!!! I hope someone has some good suggestions because this thing is making me nuts!!!!!!!! Thanks guys.

 

Is the oil clean and full? do you have access to a scan tool? Is the EBV working properly? If the oil is filthy the HPOP will loose pressure and your injectors will not fire properly. Does it sound like it's running out of fuel, or air getting in the system? Loud crackling noise from the engine. If the oil is getting hot you maybe loosing HPOP pressure. Air filter clean, no restrictions in the exhaust system, thats why you need to check the EBV. You can here it hissing under acceleration. Check engine light on? you feel the trans shift? Check to see if the cam sensor has been changed, look for a black one not gray. Let me know

 

Thanks for your quick reply! The oil is changed every 5k and is full. Please tell me what the EBV is, I'm not good with acronyms. It does act like it's just running out of fuel. I am giving some thought to the real possibility that I got a bad aftermarket fuel pump from O'Reilly. I am going to my local ford truck dealer this morning and get a real one. The one I bought sounds like a swarm of mad bumble bees. I changed the cam sensor about 6 months ago with an OEM from Ford. My experience with the cps is that it will just shut the engine off suddenly and then start back? Again, thanks for your help because this thing is about to become a flower bed: patience is getting thin!

 

UVCH possibly. What you're describing is similar to what I experienced when one of mine went bad. Under Valve Cover Harness. Solution is 50 cent mod/ New harness and valve cover gasket possibly but not 100% sure it's your problem. I knew right away because I ran dual EGT gauges and seen one bank went dead while the other spiked the gauge.

David is referring to you EBP - Exhaust Back Pressure if I'm understanding him correctly. If the EBPV - Exhaust Back Pressure Valve is staying open it will cause boost to be non existent for the most part. I do not think this is the problem since the truck runs perfectly fine for the first 10 minutes.

It sounds to be like you're throwing money at the truck and thinking you're going to get lucky. Is it throwing any codes of any kind? Just because the SES light isn't on doesn't mean that there's no codes. I would suggest you invest in the torque app and a dongle if you have a smart phone or tablet. Do a search and you'll come across Tuglys threads on it. It's extremely useful and can be a great "cheap" tool for troubleshooting.

You're not getting a lot of responses because of the little information provided. All you're providing is what you "feel and hear" sometimes that's fine but no one wants to be wrong and your issue isn't one of the "normal ones"

 

The first thing I'd do with those symptoms would be to connect a fuel pressure gauge and see what it is at wide open throttle, under load.

 

echo=on
PERFORMANCE DIAGNOSTIC TESTS (Warm Engine / EOT > 140*F)

Tools: Tools: Fuel Filter Cap Removal Tool / Flash Light / White Bond Paper / Stop or Wrist Watch w/Secong Hand Sweep / DVOM / Vacuum Pressure Test Gauge Bar #014-00761 19-0002 / Fuel Port Adaptor and Pressure Gauge 0-160 PSIG

Step #1: Visual Engine/Chassis Inspection

Tools: Flash Light

a. Fuel
b. Oil
c. Coolant
d. Electrical
e. Hoses Leaks Check

Step #2 Check for contaminates Correct Grade and Viscosity.

a. Miles/Hours on oil
b. Correct level?

Tools: White Bond paper

Step #3 Intake/Exhaust Restriction

Tools: Flash Light

a. Inspect air filter and ducts
b. exhaust system
c. Inspect exhaust back pressure device

Step #4 Intake Restriction

Tools: Vacuum Pressure Test Gauge Bar #014-00761 19-0002

a. Check filter minder or measure at WOT with magnehelic gauge.
b. Spec: Magnehelic-2"- 2.5" / Filter Minder / H20

Step #5 Perform KOEO On Demand Test

Tools: OBD-II On-Board Diagnostics, Phase 2 Vehicle Media Communications Unit (Scanner)

a. DTCs set during this test are current faults.
b. Note: IDM DTCs displayed here could be current or historical faults

Step # 6 Retrieve Continuous Trouble Codes

Tools: OBD-II On-Board Diagnostics, Phase 2 Vehicle Media Communications Unit (Scanner)

Note: IDM DTCs are cleared when codes are cleared

Step #7 KOEO Injector Electrical Self-Test

Tools: OBD-II On-Board Diagnostics, Phase 2 Vehicle Media Communications Unit (Scanner)

All injectors will momentarily buzz, then individual injectors will “Buzz” in sequence 1 through 8.

Step #8 Fuel Pressure Tests

Tools: Fuel Port Adaptor and Pressure Gauge 0-160 PSIG / DVOM

8a. Fuel Pressure at the right head

a. Verify that fuel is in the tank and the pump is being powered.
b. Measure fuel pressure at the front of right cylinder head Road Test- engine at full load condition Spec. Measurement / Head 0-160 PSI / WOT 45 PSIG min.

8b. Fuel Pressure at the left head

a. Verify that fuel is in the tank and the pump is being powered.
b. Measure fuel pressure at the front of right cylinder head Road Test- engine at full load condition Spec. Measurement / Head 0-160 PSI / WOT 45 PSIG min.

c. If fuel pressure fails low, Go to step 8c.

d. If pressure is above min. spec, Go to step 8b. 8b. Fuel Pressure at the left head

e. Measure fuel pressure at the front of right cylinder head Road Test- engine at full load condition Spec. Measurement / Head 0-160 PSI / WOT 45 PSIG min.

f. CAUTION: Secure hose away from turbo and exhaust

g. If fuel pressure is below min. spec, replace left check valve > If fuel pressure is above min. spec, Go to step 9.

8c. Electric Fuel Pump Pressure

a. Measure at fuel outlet from electric fuel pump: 45-80 PSIG > Road Test- engine at full load condition 45-80 PSIG
b. If fuel pressure fails low, Go to step 8d.
c. If pressure is above min. spec, replace right check valve.

8d. Electric Fuel Pump Inlet Restriction

a. If fuel line is restricted above 6 Hg, check for: blockage between pump and fuel tank.
b. If fuel line is not restricted, inspect regulator valve condition and for debris, If OK replace pump
c. WOT under load Spec: > 42 psig

Step #9 Perform KOER On Demand Test

Step #10 Injection Control Pressure Tests

Tools: Bi-Directional Scan Tool / Stop or Wrist Watch w/Secong Hand Sweep

10a. Injection Control Pressure Tests (Oil Aeration - Poor idle quality)

a. All acc. Off
b. Monitor ICP and RPM with Bi-Directional Scan Tool Hold engine speed at 3400 RPM for 3 minutes
c. Spec: ICP: 1800 PSI MAX @ 3,400 RPM

10b. Low Idle Stability (ICP Pressure)

a. Check at low idle, EOT above 180 F
b. Monitor ICP and RPM with the Bi-Directional Scan Tool 400 – 600 PSIG @ 670 RPM’s If engine RPM is unstable, disconnect the ICP sensor, If RPM is still unstable, change IPR and re-test.
c. If RPM smooth’s out, the ICP sensor is at fault. Note: ICP will default to 725 PSI when disconnected

Step #11 Crankcase Pressure Test

Tools: Vacuum Pressure Test Gauge Bar #014-00761 19-0002

a. Verify engine is at normal operating temp
b. Measure at oil fill with adapter and orifice tool P.N. 5631 & 014-00743 installed.
c. Block breather tube on left valve cover
d. Measure at WOT no load Spec < 3 H20

12. Cylinder Contribution Test

Tools: OBD-II On-Board Diagnostics, Phase 2 Vehicle Media Communications Unit (Scanner) / Stop or Wrist Watch w/Secong Hand Sweep

a. Verify that EOT is above 70 F
b. Turn A/C and all accessories off
c. Select Cylinder Contribution from the test menu
d. NOTE: The test will run at idle speed for about 120 sec. and no engine change will be felt during the test

13. Exhaust Restriction

Tools: OBD-II On-Board Diagnostics, Phase 2 Vehicle Media Communications Unit (Scanner) / Stop or Wrist Watch w/Secong Hand Sweep

a. Visually inspect exhaust system for damage
b. Verify EBP device is open at WOT in park or neutral
c. Monitor EBP with the Bi-Directional Scan Tool with the engine temperature at 170°F minimum at 3400 RPM
d. Spec: 34 PSI Max @ 3,400 RPM

14. Boost Pressure Test

Tools: OBD-II On-Board Diagnostics, Phase 2 Vehicle Media Communications Unit (Scanner) / Vacuum Pressure Test Gauge Bar #014-00761 19-0002

a. Verify that MAP hose is not damaged, plugged or pinched
b. Verify that intercooler hoses or intake are not leaking.
c. Verify that the green Wastegate hose is not plugged.
d. Monitor MGP (manifold gauge pressure) and RPM
e. Road Test - select appropriate gear to obtain desired engine speed and full load on engine (best accomplished climbing hill or truck fully loaded).
e. Spec: MGP 15 PSIG Min
echo=off

 

I am with John2001.That is the symptoms.

https://www.ford-trucks.com/forums/9...rpms-long.html

 

I had a very similar problem. Under Valve Cover Harness was loos and almost totally off on the drivers side. I just replaced them both with the new ones. The new ones have no under VC clips. Only clip is above and the new ones come with the pig tail for diagnosis later. So worth it. 1-2 bolts on each side was a PITA but you have that with any engine.

I think when the stuff warms up it becomes more supple and then "disconnects" just enough it does not run right. I was first kicking Glow plug codes. Before the injectors were not working 100%.

Hope this helps.

 

Thanks very much for all the help guys! I was beginning to think that this forum was just for guys that already knew everything! I am an accomplished Small Block Chevy builder and make a good living at it for circle thank cars and street rods but I'm afraid that doesn't make me an expert at 7.3 diesel engines and diagnostics. I see many people getting a little frustrated and if I may say, When someone comes to me for advice on a cam or carb combination, I do realize that it doesn't make him an idiot, it just says he hasn't yet been taught. I like to say that my Suma *** Laudi graduate son from an Ivy League school can't fly a 747 but that don't mean he's stupid. It just means he still has things to learn. So thanks again for all the help I did get and to just a very select few I might add : The lowest bum on any street corner knows SOMETHING that you don't so cut him some slack!

 

I don't see any signs of anyone getting frustrated. Have you been able to check fuel pressure yet? You can check it either at the post filter port on the filter housing, which is a -5 ORB hex socket plug low on the back of the right side near the fuel lines to the heads, or a test port on either head; 1/8" NPT plug under the compressor housing on the left head, or below/behind the A/C Compressor on the right head. The port on the filter housing is easier to get to, but will require an adapter unless your gauge hose has -5 ORB threads.

 

Sometimes you can get a shop/person around in your area to do a "Buzz" tests of the injectors. The tester it will even ID what # cyl/s. This will be a cheap way to see if the harness and injectors are all working up to snuff. Granted that would be not running but can be done HOT engine. Also a simple Multi meter test can be done on the harness above suspected side of problems. Glow plug pins, should also be giving wrong readings IE open circuits if the harness is coming apart/disconnected under the VC.


I think and correct me if I am wrong Diesels in general will use more fuel when cold. So the fuel pressure/flow when warm issue to me sounds counter intuitive.

 

Primarily, the Buzz Test should be run on a Cold Engine to identify Stiction or Solenoid issues with injectors. But, can also be used on a warm engine to identify the same as well as electrical anomalies related to the IDM and wiring.

The Fuel Pressure is very important to operation, especially under a load. A Diesel may Idle smooth with no signs of malfunction. But, under a load, additional fuel is required. Fuel delivery flow is pressure dependent. Often, the vehicle will start with a non-functioning or restricted fuel pump. However, they normally will not reach or exceed say 40 MPH. Inadequate or cavitated fuel can destroy an injector in short order.

 

Thanks guys! I think I (with some help from a really good parts man at Gator Ford) may have solved the problem!!! This truck over the years has been given several wrong parts! It is an early build but had the injectors configured for a latebuild. It had an IDM120 that should have been a 110. It had the "AD" injector in #8 which should have been an "AB" like 1-7 again because of the early build. It has been a hodge-podge of stuff put on this truck. By Monday, I will have EVERYTHING as it should be and will have done the .50 mod. I guess I'll see what happens then but I expect to have a good running truck finally. So far, PCM, IDM, fuel pump, correct injectors, MAP sensor, 27 drops of blood and 2gallns of sweat! Not to mention the cost of a small Texas ranch! But not one of the afore mentioned parts were correct for this truck (except maybe the MAP, not real sure). It HAS to be an improvement to have the right parts and computers! I just wish I had the folks that did all this in front of me so we could have a good ole KY Redneck "conversation"! On the plus side; I'm learning a lot about 7.3's. WHEW!

 

Wow! Well, at least you're getting it where it needs to be.

You're better off getting the build date / Serial# off the D/S Valve Cover for future parts purchasing. There was a lot of over lap from December 98 to March 99.

 

Neither the IDM nor the AD injector is likely to be the cause of your problems. At this point, it really sounds like parts are just being thrown at it en masse and as a result you'll probably never know which of those parts was the real problem.