Injector Problem?

[cjd]

I have the later, non-turbocharged engine in a 2008 1163. Today, all of a sudden, it started making a "squeaking" noise, which sounded like the belt was chirping. Then, on acceleration, it continues the chirping, but also started an irregular knocking. Within 5 minutes the knocking was irregular, but constant...even at idle.

I have worked on a lot of Cummins diesels, and this sounds like a leaking injector to me. Has anyone else had this problem?

 

[Mogman]

Leaking injectors are not uncommon with the Detroit.

 

[cjd]

Thanks.

So I assume the troubleshooting is the same as a Cummins…that is, block the injector lines one at a time until you find the bad one? Is there a special plug for this? Also, the usual injector shops don’t mess with HMWV injectors. Is there a decent supplier for injectors?

 

[Mogman]

Thanks.

So I assume the troubleshooting is the same as a Cummins…that is, block the injector lines one at a time until you find the bad one? Is there a special plug for this? Also, the usual injector shops don’t mess with HMWV injectors. Is there a decent supplier for injectors?

You don;t want to block the injector, just bust one loose at a time until the knock stops

 

[cjd]

I’m not sure what that means.

on Cummins you remove the hard line to each injector and plug the supply, one at a time.

 

[Mogman]

You loosen the line connection ether at the injector or the IP thus relieving the pressure on that injector until you find the injector causing the issue.

 

[cjd]

I would imagine that results in fuel spraying everywhere. I guess it would be possible to run a hose to the open line to capture the fuel? Also, are the lines separated, so that opening one will not vent all of the injector lines? On a Cummins the entire fuel circuit would lose pressure if you break open a line.

I have been watching some of the Army service videos. They make it sound like cleaning these injectors is a field operation, not requiring the injector to be flow tested or rebuilt. Is that correct, or is it recommended to send them out for rebuild or replacement?

 

[sbgarage]

Pull them one by one and pop test them is an option, but time consuming

 

[Mogman]

Done it many times and never had any issue with it spraying all over the place, it more or less just dribbles out.
The quantity of fuel injected at idle is very small.

 

[cjd]

Interesting!

The Cummins fuel rail runs as high as 30,000lbs/sqinch...the fuel spray can cut your finger off if you start reaching around a leaking hard line! Apparently the HMMWV is much lower pressure.

As soon as the weather gets below 100 degrees I will check the injectors.

 

[Mogman]

Interesting!

The Cummins fuel rail runs as high as 30,000lbs/sqinch...the fuel spray can cut your finger off if you start reaching around a leaking hard line! Apparently the HMMWV is much lower pressure.

As soon as the weather gets below 100 degrees I will check the injectors.

These are not common rail engines, 100% totally different and yes the pop IIRC around 2000psi

 

[cjd]

Well, I have to ask...what is the "pop".

 

[Mogman]

Well, I have to ask...what is the "pop".

That is the pressure the injector opens up and delivers the fuel to the cylinder, when tested they literally "pop" when they get to the firing pressure.
With common rail, at least the ones I am familiar with the injector is electrically controlled buy the ECM.
You can think of these mechanical injectors as simply a relief valve with a 1800-2200PSI set pressure.

 

[sbgarage]

Pop testers are cheap online, but its best to get a middle of the road priced unit, or even a vintage domestically produced unit. Read reviews for sure.. If you do need injectors dont fall victim to the "marine grade" option. Db2 pumps can't deliver enough fuel for the HP gain, you'd be fine replacing a single injector or two with a reman, if you're adventurous enough you can rebuild yourself. They aren't cheap! I can vouch Leroy diesel and Kennedy diesel might still have some injectors, stay away from Pensacola.

 

[cjd]

Very interesting. I may have to dig in and study this system closer. The timing must be set entirely by the "pop" pressure and the fuel pump. I can see how a weak spring in the injector would lead timing considerably. Thank you for the sources, SB!

 

[Mogman]

Very interesting. I may have to dig in and study this system closer. The timing must be set entirely by the "pop" pressure and the fuel pump. I can see how a weak spring in the injector would lead timing considerably. Thank you for the sources, SB!

Allot of things can affect timing including lift pump pressure, on these engines none of that is super critical, if you are into high performance diesels you will be VERY disappointed in any of the 70s-90s era 4 stroke Detroit (GM) diesels, none of those V8 Detroits made enough power and none were dependable enough to even justify their existence.
I have a timing light that clamps to the injector line

 

[cjd]

I do remember those diesels, all derived from gas engines, that tended to explode randomly!!

 

[Mogman]

I do remember those diesels, all derived from gas engines, that tended to explode randomly!!

You have one of those diesels, not a nickle difference between the 5.7L. 6.2L and 8.2L series engines.
The 6.2L series was only marginally better than the 5.7L series, and like most failures when they tried to improve it (6.5L), it got worse.
GEP did do what GM could not and make it a little more dependable but the basic failings of that design could never be overcome.
The "improved" cooling system flows 3 times as much water (read uses allot more HP) as the Dmax engine and does a very marginal job of cooling the 6.5L whereas the Dmax runs MUCH cooler with the same stack and body making almost 3 times the HP.
I understand they are from different generations but junk is junk, I was working as a line mechanic when the first Detroit came rolling into the Cad. dealer on the back of a wrecker in Waco TX in 1978 and then became their "diesel mechanic" as none of the old timers would touch them.
You might find this hard to believe but I am not a big fan of the "Detroit"

Edit, this was an Olds, Cad, GMC truck dealer so my experience carried over to the 6.2L when it came out in late 1981, it is also patterned after a gas engine similar to the 5.7L. I have also had several 8.2L "fuel pincher" diesels in mid size trucks and a bus, what a gutless wonder that was..

 

[87cr250r]

The injection pressure is much higher than the popping pressure. Pressure continues to rise after the injector pops open.

However, there is no risk from cracking the nut on the injector. With the nut cracked pressure doesn't rise. This is also why the cylinder shuts off, the injector doesn't pop.

 

[Retiredwarhorses]

You have one of those diesels, not a nickle difference between the 5.7L. 6.2L and 8.2L series engines.
The 6.2L series was only marginally better than the 5.7L series, and like most failures when they tried to improve it (6.5L), it got worse.
GEP did do what GM could not and make it a little more dependable but the basic failings of that design could never be overcome.
The "improved" cooling system flows 3 times as much water (read uses allot more HP) as the Dmax engine and does a very marginal job of cooling the 6.5L whereas the Dmax runs MUCH cooler with the same stack and body making almost 3 times the HP.
I understand they are from different generations but junk is junk, I was working as a line mechanic when the first Detroit came rolling into the Cad. dealer on the back of a wrecker in Waco TX in 1978 and then became their "diesel mechanic" as none of the old timers would touch them.
You might find this hard to believe but I am not a big fan of the "Detroit"

Edit, this was an Olds, Cad, GMC truck dealer so my experience carried over to the 6.2L when it came out in late 1981, it is also patterned after a gas engine similar to the 5.7L. I have also had several 8.2L "fuel pincher" diesels in mid size trucks and a bus, what a gutless wonder that was..

yea, it’s such a crappy engine it’s still being produced today…42yrs later.