LLY: LLY surging

[joshd472]

I hope this is the right threat. Please forgive and move if it is not.

My 2004.5 lly has a slight surge at idle and 99% of what i have read says it the FPR. I took it to a shop where a guy did a fuel return test on it with a snap-on scanner and said all of the injectors were bad on the passenger side and that he wouldn't waste time with the FPR.

The truck runs fine other than a surge at idle and has no smoke. My question is my mechanic correct? Could something cause bad readings on his test like at air leak?

I'm not saying i don't believe they are bad but i would just like to rule out any possibilities before i spend a pile of money on injectors.

 

[six5creed]

Has the truck been ice picked?

 

[joshd472]

It has not. My plan was to to ice pick and replace all flexible fuel lines before i order injectors. It's not a daily driver so I'm not putting any hours on it right now.

 

[Chevy1925]

LLY injectors with high return rates are common when they have high miles on them. they could very well be the issue with your surging too and will not give the typical warning signs. A return rate test is not the difitive way to know if it is for sure the injectors or FPR causing the surge though. he needs to see what the main mm3 fuel rate is at idle (and you should have the stock tune in it if you dont already). if its down to 2-3, it will cause the surge you are getting. if it is not, he needs to watch the rail pressure for variance between desired and actual pressure. he did not do a thorough diagnosis

 

[joshd472]

LLY injectors with high return rates are common when they have high miles on them. they could very well be the issue with your surging too and will not give the typical warning signs. A return rate test is not the difitive way to know if it is for sure the injectors or FPR causing the surge though. he needs to see what the main mm3 fuel rate is at idle (and you should have the stock tune in it if you dont already). if its down to 2-3, it will cause the surge you are getting. if it is not, he needs to watch the rail pressure for variance between desired and actual pressure. he did not do a thorough diagnosis

Thanks for taking the time to help me out. He said if it was a FPR it would be throwing a code. I do have the stock tune on the truck.

 

[joshd472]

Chevy 1925 one thing I forgot the truck has a bully dog programmer and I'm not sure if he uninstalled the tune before doing the return test. I have since uninstalled the tune but I still have it plug into the truck. It's basically gauges at the point.
Anyway it does measure my ICP. At start up I hover around 5ksi. Then once the truck warms up it goes down to around 3ksi and spikes up to 7ksi then back to 3ksi for around 10 seconds or so then spikes back up to 7.

I've drove the truck around the block a couple of times and once I get back to the house the surge is different (sometimes) it's more of a continuous slow surge if that makes sense. The truck will slowly fluctuate up and down around 50 rpms and the ICP pressure will slowly go between 4 and 6ksi.

I have no idea if the ICP pressure has anything to do with my problem. Thanks for all the help.

 

[Chevy1925]

the bully dog wont affect a return rate test and a bad FPR wont always throw a code. your mechanic doesnt know what hes doing if thats really what hes telling you.

no idea what the ICP is. the numbers seem like rail pressure but until i know what ICP stands for, cant be sure. We also need to know the main injection fuel rate as well. it can make rail pressure dance like a bad FPR would if the injectors are indeed returning way too much fuel.

 

[joshd472]

the bully dog wont affect a return rate test and a bad FPR wont always throw a code. your mechanic doesnt know what hes doing if thats really what hes telling you.

no idea what the ICP is. the numbers seem like rail pressure but until i know what ICP stands for, cant be sure. We also need to know the main injection fuel rate as well. it can make rail pressure dance like a bad FPR would if the injectors are indeed returning way too much fuel.

I THINK ICP stand for (injector control pressure) but don't get me lying. I know it's fuel pressure but I don't know where it is reading from. I will try and do some research to find out.

My plan for this weekend is to replace the fuel lines and a couple of other things to rule out an air leak. Pull, inspect, and clean injectors. Is there any thing i can do to test the FPR? I would like to rule that out before I replace injectors.

Am I wrong in thinking that if I had 4 bad injectors the truck would run like absolute shit? It doesn't seem down in power compared to my father-in-laws LB7

 

[Burn Down]

Since when can a snapon scanner or any scanner for that matter, read the fuel return on each injector?

I would think he was reading balance rates?

You most certainly can diagnose bad injectors with just a return rate test but it has to measured into a graduated cylinder per injector.

 

[Chevy1925]

I THINK ICP stand for (injector control pressure) but don't get me lying. I know it's fuel pressure but I don't know where it is reading from. I will try and do some research to find out.

My plan for this weekend is to replace the fuel lines and a couple of other things to rule out an air leak. Pull, inspect, and clean injectors. Is there any thing i can do to test the FPR? I would like to rule that out before I replace injectors.

Am I wrong in thinking that if I had 4 bad injectors the truck would run like absolute shit? It doesn't seem down in power compared to my father-in-laws LB7

im trying to help you actually diag the truck for a problem BEFORE you throw money at it hoping for a fix. you can have a high returning injectors and the truck still run like new till you start asking for more fuel than the stock cp3 can supply because of the returning fuel.

until you can get me the info needed, we wont be able to rule anything out.

 

[joshd472]

Since when can a snapon scanner or any scanner for that matter, read the fuel return on each injector?

I would think he was reading balance rates?

You most certainly can diagnose bad injectors with just a return rate test but it has to measured into a graduated cylinder per injector.

You correct. He was giving me balance rates, but he also did a fuel return test.

 

[joshd472]

What is the cheapest scanner I could get so I can check the rates myself?

 

[joshd472]

im trying to help you actually diag the truck for a problem BEFORE you throw money at it hoping for a fix. you can have a high returning injectors and the truck still run like new till you start asking for more fuel than the stock cp3 can supply because of the returning fuel.

until you can get me the info needed, we wont be able to rule anything out.

Ok so I done some research and I'm pretty sure the ICP gauge is my rail pressure. You need main injection fuel rate, correct? Is there anything else?

I pulled the injectors this weekend. I had already taking a bunch of parts off the truck and they were easy to get to so I figured what the hell. One of my return line fittings broke off at the O-Ring and my local auto store had to order that and the copper seats so unforantly I didn't get to do the cleaning process.

 

[WVRigrat05]

If it already have them out, just send them out to get cleaned and tested. Then you'll know for sure what you need

 

[joshd472]

If it already have them out, just send them out to get cleaned and tested. Then you'll know for sure what you need

Where could I send them? What is the cost and turn around time? Sorry for my ignorance. I'm new to diesels.

 

[WVRigrat05]

I send mine to ksd diesel in WV and they then sent them out, it was 300 bucks.
Second time the guy that built my motor took care of it.

Exergy does it for around 350-375, and has a better testing set up.

There's several others,

Get ahold of Lincoln diesel and see how long it takes them.

Most places are two weeks to over a month just depends.

I never pull injectors without having them tested. 300 bucks is cheaper than the time it takes to do it twice

 

[joshd472]

https://m.youtube.com/watch?v=X6h5uKLYIQk

So i ruled out an air leak. I haven't gotten to try doing the cleaning yet. I found this video last night and this is EXACTLY how my truck is acting.

 

[joshd472]

I replaced the FPR and the problem is gone.