engine hesitation...

[toddg58]

engine hesitates sometimes cruising and sometimes under acceleration. sometimes it will go a couple of days without doing it. seems more noticable when running the air conditioner. any ideas?? I have had my 6.5 for 2+yrs all stock 145000 miles. Any help would be greatly apreciated.... thanks in advance to everyone....

[3bals]

Mine will act that way when the fuel filter needs changing.

Jody

[toddg58]

I have only about 5 thousand on it since I changed it.

[3bals]

You may have purchased some substandard fuel. I know there are many things that can cause a hesitation or as I called it a "studder". A weak or non operating lift pump, a clogged pick up screen/sock and or your IP. Start eliminating things. Check the fuel pressure at the bleeder petcock. I believe it should be 3-5 psi.

I changed a fairly new filter once, only to find that it wasn't my problem. I saved it wrapped in plastic and in a sealed container. I was able to use it again at a later date with no problems.

Read some of the other posts on this subject here to see what others had to say.

Jody

[toddg58]

I guess the thing that got me was that it is not all the time..... it will do it for a few days then not do it.....

[sixnickel]

I agree with 3bals about the fuel filter and pressure.
I don't care if the fuel filter is a week old. If you get a bad load of fuel you can plug a filter in no time. Let's say you are fueling up as the tanker is making a fuel drop or he just left before you pulled in, the tank is all boiled up and crap in the bottom all mixed in with the fuel you just bought!!

[grancito]

When you run the air conditioner, the under hood temps increase, where is Your PMD located? See mine inside the bumper, passenger side.

[toddg58]

it is still in the stock location. I have not done any mods at all. it is bone stock. I will also check the fuel filter.... should I buy a new one and relocate it??? like from ssdiesel supply....

[grancito]

look at my PMD removal tool posted Sunday, and PMD relocation a few days back, you need a heat sink. I was begining to have hard starts hot with a new PMD on a heat sync- SS DIESEL on the manifold and so moved it to the bumper and now no problem.

[toddg58]

it starts right up when hot..... I have not had any issues with it starting yet...

[horsehaulin]

I would start looking at your lift pump and OPS (oil pressure switch). When the engine is running at idle in you drive way and you open the fuel drain petcock. Does the engine stuter and die, or continue running like a champ? This test is not 100%, but helps in the diagnosis. Another way is to start the truck crawl under the drivers side door, unplug the lift pump and check for voltage with a test light or voltage tester.

Hope this helps,
Tony

[toddg58]

I guess I will try a lift pump..... the thing that gets me is that it is sooo spuratic....about when it happens....

[mangus580]

If it were me, I would replace and relocate the PMD first. Your description sounds classic PMD failure....

[w_huisman]

What year truck are we talkin about here? Any codes? SES light ever on?

Don't just throw parts at it. If you want to throw money around, throw some our way. I'm sure most of us here will take pay pal, credit card numbers, or any other way you perfer to pay us. ;)

Do as horsehaulin says. Open the fuel filter drain when the engine is idling. Does it spit, sputter, and die, or does it keep running while dumping fuel on the ground? if you have the means, and if your engine doesn't die during the previous test, put a fuel pressure gauge on the end of the drain valve and check fuel pressure at idle. 4psi or better is good. Anything less is suspect.

If the previous two test results are good, check for air in the fuel lines by routing a clear 3/8" tube from the fuel filter housing discharge to the IP inlet, around the outside of the intake. Idle the engine and watch the clear tube for air bubbles.

Your problem could be fuel line leak, could be pmd going south, could be intermittent OPS operation, could be a bad injector, could be..... blah blah blah You get the picture. Patience and diagnosis will cost you much less than frantic parts replacement.

Check for codes and run these tests. Post back here afterwards.

[toddg58]

well I made a 4hr trip yesterday and I ended up getting a SES light which has already went out, but it popped 2 codes. They are P0126 and P0236. could anyone help me with this???? thanks.....

[grancito]

All I can give is what the codes refer to. PO126 insuficient coolant temperature for stable opperation. PO236 turbo boost sensor A circuit, range or performance problem. Someone else will have some suggestions where to look for a fault. Take a look at MPG,Power, stall, whatsup, post on it today.

[toddg58]

well i ordered the two parts to fix the codes and will install them and see what happens. Maybe it will help fix the original issue, but I doubt it... only time will tell....

[toddg58]

I was driving home from work today and it shut off twice. the first time it took a few min to start back up, and the other time it started after I put it in neutral and turned the key.... is this a pmd going bad???

[toddg58]

Here is what I know so far.... the fuel comes out of the filter bleedand does not make the engine die.... when it quit last night it did not have a SES light come on. I replaced the waste gate solenoid because of the 236 code and it has made a difference in performance. I just went and had the codes read again just in case and there is none. I am new to diesels so I am just trying to get an idea of what is causing it to stall. It is my primary mode of transportation, so I am just trying to get it fixed..... thaks for the help to everyone....

[crazy]

i got the same problem with my truck and the same codes reading

P0216 i was told it had something to do with injection timing control malfunction and code P0238 was tubo boots sensor

now here where i stand i have hard time believing it a pmd cause there days the truck run fine for 5 or 6 days and there time it juat stall then there times it it start right up as soon as u put in drive it stall. my truck been acting this way for about 5 or 6 months

Am i right that the PMD is a computer, am if i right wouldnt it give u a problem all the time? just like a home puter would!

[toddg58]

I had a 126 which is a coolant sensor and a 236 which I changed the waste gate soleniod for. My truck just started to stall yesterday, but before that it stumbles a couple of times every few days, but not all the time. The PMD is a pump mounted driver.

[crazy]

sorry about that, i reaad the code wrong that what i get for not putting my glesses on

[w_huisman]

Here is what I know so far.... the fuel comes out of the filter bleedand does not make the engine die.... when it quit last night it did not have a SES light come on. I replaced the waste gate solenoid because of the 236 code and it has made a difference in performance. I just went and had the codes read again just in case and there is none. I am new to diesels so I am just trying to get an idea of what is causing it to stall. It is my primary mode of transportation, so I am just trying to get it fixed..... thaks for the help to everyone....

Stalling with no codes is definitely a symptom of pmd failure. The only way to test for pmd failure is to install a known-good pmd.

If you wish to verify for certain that there is not air in the lines, run the clear tubing from the fuel filter discharge to the IP inlet, as previously suggested.

Otherwise, your next step is to try a good pmd. It becomes quite a predicament if you can't borrow a known good pmd and your only option is to buy one. It is hard to spend $200 - $300 on a new pmd when it will possibly not solve your problem, so you may wish to buy a used-but-good pmd off the big auction site first.

IMO, the best route is to buy a used-but-good pmd to test. If it proves your pmd is the cause of your problems, then (for reliability) buy a new pmd from the dealer, extend your existing pmd harness by splicing in 5 - 6 feet of 14ga. wire, buy a cooler (not the blue one on the auction site), and mount that new pmd on the cooler somewhere outside the engine bay. Put the "good-but-used" pmd in the glove compartment as a spare (every 6.5TD owner should have one).

IMO you're wasting your money if you mount a pmd & cooler inside the engine bay (especially on the intake). If you do not want to move the pmd to outside the engine bay, the next best place for it is on the side of the pump where GM originally put it. If you are diligent about checking for proper lift pump operation and letting the engine cool before shut-down after a hard run, a pmd on the side of the IP will last a long time.

[grancito]

I agree with the relocation out side the engine compartment, it is an easy change to put it in the bumper, SS diesel heatsync will screw into the upper lip of the bumper with 2 self drilling roofing screws. See my post "PMD relocation". Also see my post "PMD removal tool" to have the spare from the pump.