How long and how much does a fuel injector contribution test cost ,I need to check my injectors as I'm starting to get a little fuel i my oil ? Also when cold get a tap,as soon as truck is warmed up tap goes away I have checked the valves and set them to spec any other thought.My oil analysis showed 3 % fuel in 7500 miles of use thats how I know I got fuel in the oil.

 

Listening for an answer to the "tapping when cold" bit.

 

At this point you know you have at least 1 bad injector. Would it be practical to test and find out you need to replace them or just replace them? I've also heard where 1 get replaced, then a time later another, then another.

 

I'm pulling all mine Monday tonight tested. But will test the solenoids first. Having a hard start and no starte issue. But no fuel in oil. I think fuel in oil means bad tip. I'll prob just replace bad ones.

 

Contribution test, they can have it whipped out in an hour, give or take 15 minutes. In other words, $70-$100.

 

Would a contribution test show a bad tip or does it have to have a bad leak to plike a cracked body? Does anyone know if the cummins shop tests injectors ?

 

They kill the injectors, one by one, and measure the percent of RPM drop for each cylinder and compare. Basically if they are all contributing equally the RPM drop for each will be the same.

Where do you live? I live within 240 miles of a shop that has a test bench. Cummins doesn't have one, as far as I know. F1 in Salt Lake City has one.

 

50 miles north of chicago,I found one place huckstorf diesel.

 

Give em a shout, see how backed up they are. Not sure if your truck is a daily driver, or one you use for a business is what I'm getting at.

 

A kill test is used to trouble shoot misfires and problems like that. The contribution tests attempt to measure the amount of fuel being injected in each event to determine if the injector is functioning correctly by comparing rpms before and after. Sometimes all you can se is a 10% variation on a cylinder to determine if there is a problem.

Depending on how far off the percentage is and which way will indicate the problem area, too much or too little fuel.

Not going to tell you much about hard\no starts. For that you need a return flow test and way to monitor demanded rail pressure vs actual. If you have a hard\no start condition it should hso win a return test and will be internals worn and that means all the injectors.

If you have intermittent rough idle problems, drop in mpg, excess smoke at cruise or hard acceleration that could be a coil or other internal injector issue. Normally the coils going bad are going to give codes. If they all test out around .5-.7 ohms resistance they are good.

Before I did anything more I would get a cylinder contribution test and an injector return flow test WITH the printouts and numbers to look at. Too many times the techs run the tests and just good\bad. Tells you nothing, make sure you get hard numbers on cc's and seconds and hard numbers on all cylinders.

Once you have that then you can better decide what to do.

 

That's the weird thing truck runs great idles great,only have the tap when cold and goes away when hot .Oil analysis showed 3% fuel in oil after 7500 miles that's why I'm looking at getting these tests done just to see if maybe only one injector is bad.

 

I am not sure the 3% after 7500 miles is even out of spec. I want to say 2-3% is normal with more than 5% an area for concern but not positive anymore. These emissions engines always end up with more of everything in the oil because they run fuel rich by design.

 

Blackstone is the one that flagged it ,I know my sample from last year had less than 1 % but I was dong 5000 oil changes and now went to 7500 OCI .

 

Any Update on this. I have the same tick also. Seems to be blowing a little more black smoke than usual. Just a little.

 

No , not yet haven't been able to leave the truck at dealer for the day.Hoping by end of next week if work can slow down for the holiday coming up.