Ford 7.3 boost questions Lack of power (1998 E350)

[Ozrockrat]

OK Guys

The Ambo is a dog. Looks like the max boost I am getting is about 8 PSI and then it goes downhill quickly.

Original problem was it would be OK (no real power but it drove OK) until it warmed up then there would be a big puff of smoke under the doghouse as one of the up-pipe gaskets let go. I managed to do a boodge repair on that as the up-pipe was scored along the pipe where the gasket runs (Ford/International what the hell were you thinking). While testing that I also dropped the exhaust before the CAT to try and rule out a blockage on the exhaust. Air filters are clean and there are no obstructions in the air inlet and no visible leaks on the compressed side.

So that one is fixed but some of the same symptoms are there. Surging, Power tapers off(actually drops off). No real get up and go.

Here is a recording of the Boost, Exhaust Back Pressure, Throttle Position and Engine RPM. It is easy to see that the boost is only getting to 8 PSI and the back pressure is fairly stable for the boost that is there.

Any suggestions before I pull the turbo and up-pipe. (Up-pipes will be replaced but I want to do something about the design before I put new ones in). (Also I am heading off to do a border to border run. AZ to Vancouver in two weeks :Wow1

 

[nely]

That exhaust back pressure reading looks odd. Its reading atmosphereic pressure 14.7 during that freeze frame.

I know my 96 & 97 dont have wastegates and assume yours doesnt. I believe its a van thing, but just incase does it have one?

Scan it and i bet youll have a exhaust back pressure sensor code. I know the sensors can carbon up and stick. And the pipe going from the passenger manifold up, to the ebp sensor will get clogged. The epb sensor is behing the hi pressure oil pump reservior.

I had codes stored on my van and the mil never came on. I happened upon this when just scanning my van to make sure everything was kosher.

 

[nely]

Btw what program are you running to get that data? Is it laptop based?

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[nely]

heres a list of what the voltages should be during all the different operations that the engine will see.

as you can see the ebp sensor should read .8 to 3v during engine operation depending on certant conditions. your is biased low, so i would start there

 

[thetonka]

Two things to look at. Now I preface this by saying my knowledge is about my 2001 7.3L in my F350, but some of the basic concepts are the same on the earlier 7.3L powerstrokes.

There is an Exhaust Back Pressure sensor on the engine. It should be attached to a tube near the front of the engine that is a take off from the Passenger side Exhaust manifold. The tube can get clogged with soot and prevent the sensor from reading correctly which will cause all kinds of problems with power and performance. The tube can be very difficult to get off and they like to break. If you can get it off check and see if it is clogged and clean it out, replacing the sensor is also a good idea. I think mine needs to be replaced.

For the exhaust manifold to the turbo this is a very common problem. It is not really an international problem, because International used bellowed up pipes that did not have the crappy donuts in them. I have had to replace or tighten the donuts in mine too many times, and I have had to replace the pipes due to holes in the pipe. Soon I will be replacing the entire assembly with a set of the International Bellowed up pipes.

These should be the ones you need if you have an early 99 7.3L.
http://shop.strictlydiesel.com/store.php/products/OBS_E99_Bellowed_UpPipes

Good luck and if you need any powerstroke specific information I have found that powerstrokenation.com is a fantastic forum for information.

 

[Ozrockrat]

Auto Enginuity

Btw what program are you running to get that data? Is it laptop based?

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Autoenginuity with the enhanced ford package. About $360.

 

[Ozrockrat]

Bellowed up-pipes

Soon I will be replacing the entire assembly with a set of the International Bellowed up pipes.

These should be the ones you need if you have an early 99 7.3L.
http://shop.strictlydiesel.com/store.php/products/OBS_E99_Bellowed_UpPipes

Good luck and if you need any powerstroke specific information I have found that powerstrokenation.com is a fantastic forum for information.

Wow they are proud of those pipes. I may have to investigate the same idea but using flexible coupling and just welding up the clamps (and use a solid steel gasket. Something like these [ame="http://www.amazon.com/Stainless-Flexible-Exhaust-Coupling-Interlock/dp/B002SSP142/ref=sr_1_4?ie=UTF8&s=automotive&qid=1305244521&sr=1-4"]Coupling[/ame]

 

[nely]

Autoenginuity with the enhanced ford package. About $360.

That will be my next purchase!!

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[thetonka]

Wow they are proud of those pipes. I may have to investigate the same idea but using flexible coupling and just welding up the clamps (and use a solid steel gasket. Something like these Coupling

There are a handful of companies that are selling those parts. If you dig deep enough you can find the International part numbers for them and try and order them directly from an International parts counter. When Ford put the International Diesels in their trucks they changed a few key things, all of which sacrificed reliability for performance gains expected in the light duty consumer market.

The 7.3L is still one of the most reliable light duty diesels ever made.

 

[Ozrockrat]

OK more analythical ****e since I am not home to work on it.

Here is the graphing of the tests I ran the other day when I was traveling down the interstate and tramped it. It ran up to about 76 MPH but then started slowing down and no amount of right foot pedal tramping made a difference.

From the graphs it looks to me like I am getting fluctuations on the EBP readings. It does not appear to be dumping the back pressure completely as it was when the up-pipe was leaking under boost.

My plan for the weekend is to replace the Cam Position Sensor (under $20 so why not). Replace the EBP Sensor (Exhaust Back Pressure) and clean the EBP tube. After these I will test it again then start looking at the exhaust/up-pipes/turbo.

Legend

Graph

 

[Ozrockrat]

New Up-pipes, exhaust wrapped, new EBP.

OK just to keep a full record here in case others have the same problems.

I decided to just replace the up-pipes with factory new ones. $197 later without the gaskets OUCH. If you check the photos below you will see how the ends of the pipes scour out letting the exhaust flow from the manifolds to the turbo escape. This is a poor design and I will be trying to use the old pipes to fab up an alternative.

Anyway I pulled the Up-pipes and the downpipe. Had a peek at both sides/internal of the turbo (no wear or feathering on the vanes. Spins freely).

Decided to give the missus an early birthday present and wrap the pipes to try and keep a bit of heat off her legs.

I also pulled the EBP (Exhaust Back Pressure) sensor and replaced it with a new one. Drilled a bit of weed eater cord down the pipe to check for blockages. New air filters as well. Along with putting the leaf blower into the exhaust (where the downpipe connects) to see if there was any restriction in the cat or muffler.

Quick test run tonight to heat the wrap and get the paint fumes out. Tomorrow I will hook up the analyser and see if there is any improvement.

I also have a Cam Position sensor on hand as the next bit to be changed.

 

[Ozrockrat]

Ok Some more progress. So just to keep the thread complete.

Pipe replacement has stopped the exhaust leaks. Wrap seems to have made it quieter. But it is still under powered. Not as bad but still stumbles when it gets down the road and then power drops off.

Replaced fuel and air filters. What a pain the fuel filter is. There will be an inline filter near the tank with a good quality spin on filter in the near future.

The filter change did give marginal improvement (old filter was very black). The previous owner thought it had a filter change at the last service. I think he may of been ripped off or there is oil getting into the fuel somehow? Having never worked on the Navistar/PSD before I need to investigate if there is a way for that to happen.

So after that I replaced the Cam Position Sensor. That also gave a minor improvement. I can now run at 55 without a problem. When I try and push it along at over 65 it starts to shudder and loses power.

Tomorrow will be the start of investigating the injection side of things. Some initial investigation reveals that these motors are know to have issues with the injector harness (under the valve covers). So I will meter those out and also do a run with the analyzer on to check IPR and the HPOP pressure.

 

[nely]

The fuel injectors use oil pressure to pressurize the fuel thats in the injector. It the multiplys fuel pressure to get the proper pressure and fires the fuel. If oil is getting into fuel id suspect injector cups. Never changed them but i hear its no fun.

Have you ran a koeo or koer test? That will help with the diagnosis. And a cylinder balance test.

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[Ozrockrat]

KEOR and KOEO both clear and Cylinder Contribution Test passed OK.

Thanks mate.

Have you ran a koeo or koer test? That will help with the diagnosis. And a cylinder balance test.
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But they were run cold. I will get out there and check the wiring harness when the sun is up. That could give me an indication. As much as it irks me I may have to take it into a shop to get looked at. I only have 10 days left until we head off and I will be working away for 5 of them.

 

[nely]

The wiring harness and connectors that go bad are the ones at the valve cover gasket and the harness underneath the valve covers.

If they cause a problem the injectors wont fire and youll have a definitive missfire.

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