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Common Rail Cummins guys...I need some help.

BustedCrank

Webwheeler
Joined
May 20, 2020
Member Number
806
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In the rain
Trying to figure out my dad's long crank/no start issue. 07 5.9 Cummins has a smarty tuner on it.

It began doing long cranks before firing off, 5, to 10, to 20 seconds. Once started it would run perfectly fine. Eventually it got to where it wouldn't start before killing the batteries. Would usually start faster once it was warmed up, but the next day would be long crank again. It eventually wouldn't start for him at all.

Went down to take a look at it, could hear the factory lift pump in the tank running as it should. Pulled a line to make sure it was getting fuel to the cp3, it was.
Smarty says it had 0 rail pressure while cranking,
Pulled the FCA and could hear the rattle when I smacked it on my hand, put it back in, and after another 10, or so, seconds of cranking it built up rail pressure and fired off.
Let it sit while, and it wouldn't start again. Pulled the FCA out again, noticed you could hear fuel moving in the lines somewhere like it released a vacuum or somehting, probably nothing, but made me wonder. Put the FCA back in, it fires up again. So we ordered an FCA.

The next weekend dad throws the new FCA in and it fires up, but the next day, nothing. So he pulled it out, put it back in, it fires up, and he drives it up to my place 2hrs away no issues.

I get the fittings and do return flow tests. R&R the FCA again to get it to fire up initially, then let it warm up to operating temp. After the initial start, started no problem during all these tests.
Pressure relief valve test...Passed, no fuel coming out of it.
CP3 pump return flow...passed, about 700ml,spec says good up to 1000ml per minute.
Injector return flow...Passed, got about 90ml, spec says good up to 180ml per minute.

So what am I missing?

Ive seen some people say there's an updated injector return flow test where you test for 30 seconds at 20k psi of rail pressure. But when I've seen the quotes they use, it states for a 6.7, not the 5.9, so I'm skeptical that it is for the 5.9. I'm just going off the factory service manual, but don't know when it was published. It states warm engine, at idle for one minute.

Another thought is the rail pressure sensor, it could be not reading correctly at first. Seems odd that it would work normal once its fired up. it reads +/- 500 within desired rail pressure when its running. Plus the fact that the truck always starts easier if you pull the FCA out, and put it back in.

Seems like an injector, or connecting tube issue, but the injector return test should have been a lot worse then it was if that were the case. I'm probably going to retorque the connecting tubes just for the fun of it.

No codes, no smoke when it fires up, runs just fine when it starts, no fuel on the oil. Using the smarty to see rail pressures.

Ideas?
 
Sounds like classic connecting tube issues to me, I'd torque those before getting too deep into anything else.
 
Sounds like classic connecting tube issues to me, I'd torque those before getting too deep into anything else.
Re-torqued the tubes, they were all tight, no change to return flow numbers.. I was hoping this was the culprit.

How many miles on the injectors? If they have 150k or more check the resistance on each one.

3 are original with 210k on them, other three have probably 50k on them.

During all the return flow testing and torquing of the connector tubes. i noticed it was starting really nicely while both batteries were hooked to my blazer. Was thinking no way it could be that easy, cleaned up the terminals, checked the cables. But I could unhook the jumper cables, it would take about 5 seconds to light off, hook them up, would fire up within 2 seconds. You could hear the difference in cranking speed. Was convinced a new set of batteries would do the trick, so I let it sit overnight, then the next day hooked it up to the blazer without it running just to see if it would start...nope. Damn.

So I decided to cap an injector line off, first one, lights off real quick...dang, injectors it is.
 
Re-torqued the tubes, they were all tight, no change to return flow numbers.. I was hoping this was the culprit.



3 are original with 210k on them, other three have probably 50k on them.

During all the return flow testing and torquing of the connector tubes. i noticed it was starting really nicely while both batteries were hooked to my blazer. Was thinking no way it could be that easy, cleaned up the terminals, checked the cables. But I could unhook the jumper cables, it would take about 5 seconds to light off, hook them up, would fire up within 2 seconds. You could hear the difference in cranking speed. Was convinced a new set of batteries would do the trick, so I let it sit overnight, then the next day hooked it up to the blazer without it running just to see if it would start...nope. Damn.

So I decided to cap an injector line off, first one, lights off real quick...dang, injectors it is.
I had one go open circuit and the others had three to six times the normal resistance. New injectors from BBI and it runs like new.
 
I didn't even test the solenoids, because when it starts, it runs just fine. Last time it lost a solenoid it was pretty obvious. When one goes open, usually throws a code, and then the computer shuts down those three cylinders. Either the front or back three, whichever has one out of its range. Solenoids are a much easier fix for sure, 60 bucks, an hour of your time, and back in business.

He's picking up new injectors and tubes from BBI tomorrow.
 
I didn't even test the solenoids, because when it starts, it runs just fine. Last time it lost a solenoid it was pretty obvious. When one goes open, usually throws a code, and then the computer shuts down those three cylinders. Either the front or back three, whichever has one out of its range. Solenoids are a much easier fix for sure, 60 bucks, an hour of your time, and back in business.

He's picking up new injectors and tubes from BBI tomorrow.

Did that fix it?
 
If he bought BBI's he is probably still waiting to get them :lmao:....you have to pay and wait for quality 3RD Gen injectors
 
When I bought my set from BBI they were on my doorstep within days. Maybe I was just lucky.
 
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