Occasional crank no start?

[dunk]

'86 6.9 with Banks, according to PO odo has not rolled and shows ~85k miles. The past week or so the truck has occasionally been hard to start. It will crank fast like normal but not fire for 20-40 seconds of cranking in 2-3 cycles. When it fired it runs normal, no missing. I am suspecting injectors may be nearing end of life as it has knocked a couple times like a stuck injector maybe or firing early.

The first time it did this was a week or so ago and was a tank venting problem, tank had a vacuum. Tank is now venting properly but still it will crank a long time before starting. Every time it has done this is when at operating temp and has been off for 20-40 minutes, though not every time. Seems to do it more frequently if parked on an angle vs level, or could be coincidence or me being crazy. On a cold start every morning or after sitting for many hours it has always fired off right away. Only time I've had hard starts is with temps around 0* this winter, and that turned out to be a loose connection on my second battery resulting in it cranking over slowly.

I'm thinking air in the system maybe return caps not sealing and the vacuum in the tank found a weak point to pull air? Or could be the pump getting ready to fail, not sure of symptoms? Something else?

 

[franklin2]

It would not be air. That would show up worse sitting overnight, giving the air more time to enter. If I remember right, hard starting when warm usually points to a injection pump problem.

Since it's intermittent, you might want to "shock" the injection pump. By that, I mean warming it up, shut the engine off, take the fuel filter off and dump the fuel out, and re-fill the fuel filter with some sort of fuel treatment, or some people use a homemade concoction of auto tranny fluid. They then run the engine for a minute, shut it off and let the concentrated treatment sit in the injection pump and the rest of the system and let it loosen things up.

 

[riotwarrior]

....I am suspecting injectors may be nearing end of life as it has knocked a couple times like a stuck injector maybe or firing early....

..... Every time it has done this is when at operating temp and has been off for 20-40 minutes, though not every time.

On a cold start every morning or after sitting for many hours it has always fired off right away.

...... Or could be the pump getting ready to fail, not sure of symptoms? ....

Good morning,

I'd suggest keeping a 2L soda bottle full of cool water with you, and next time this occurs to pour it over the head of ip where the lines come out. This will COOL it down quite a bit, and cause it to shrink some, if it fires right after doing this, then your IP is on it's way out.

This is a common symptom of a worn pump where when cold it pushes enough fluid at a high enough pressure however tolerances stack up over time and wear and so forth cause the failure you are describing.

There are plenty of threads on this exact subject.

I'd suggest it's time for a replacement pump soon so budget for it.

Contact Mel at www.conestogadiesel.com or if you are out west contact Russ, aka Typ4 via PM and he can help you too.

JM2CW

Al

 

[Ugly Moosling]

I agree with Al about trying to cool the pump down and see if it will start Typically hard start hot does point to the injection pump but another possibility is a weak lift pump or starter.

 

[dunk]

Finally did another crank no start. At a rest stop about 200 miles from home and towing on the highway for a couple hours, not where I wanted to be stranded! Usually it would fire within about 30 seconds or so either pedal at idle or wide open. Wasn't giving me anything the other day after a few cranking cycles, so I poured a bottle of water over the pump and it fired off as soon as I turned the key. Looks like new IP time, may as well do injectors and return lines too. For now I'm just keeping a few bottles of water in the truck and just need it to last a few weeks until I get back from vacation.

Also first time I did long distance only towing. '86 CC 4x4 6.9 with Banks, C6, 3.55:1 stock height/tires, timing at 9* pulse method, towing about 5000 lbs and a few hundred pounds of stuff in the bed. I was a bit disappointed with the MPG of 10.91. 536 miles of highway towing mostly at 65 MPH. A little bit of traffic and stop and go, and a bit of 70-75 (downhill, trying to keep it rolling for the next uphill). Hills were terrible, slowed to 35 MPH a few times on long hills. It seemed like it would maintain about 40 on the longer steeper hills but EGT would be knocking on 1000 and I'd have to back off before the top, don't want to push any further with the probe at the pedestal. Will a new IP and injectors from Conestoga Diesel help with the performance? If so will it end up being a wash as EGT may rise faster?

My old 460 truck (3.55:1, 35" tires, ZF5) could pull all these hills in this exact same route with same load at 65-70 MPH just downshifting to 4th and letting it rev. A few very steep hills on two lane blacktop it had to work really hard in 3rd but it would keep up with traffic fine and I was always passing the big trucks which crawl up these hills. The gasser got 10 MPG doing the same job and pulling faster. With diesel a few cents more than 93 octane the cost per mile is about the same. Would just like to be able to hold normal speed on anything but the steepest hills. Did not expect it to be this bad with a fairly light load, hoping a new fuel system will make a noticeable difference. The plus side is now driving around town without the trailer the truck feels real fast.

 

[79jasper]

With that c6, you probably won't get much better mileage.
But you can get the power back with a new injection system.

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