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Thread Title:

Fire Truck 6V92 DDEC

Created On Thursday December 25, 2008 09:38

GoneFishen

Posts: 1325
Joined: Jan 2007

Thursday December 25, 2008 09:38

Customers complaint low power. This truck takes 18 seconds from a stop to travel 250 ft. [80m]

This is what I have had checked and/or performed: This is a DDEC 3 engine, timing wheel was checked on the front of the LB cam, gap checked, cylinder cutout checked, injector response time ok, injectors pop tested-1 failed-replaced all 6 retuned and replaced fuel filters, air filter checked, turbo checked both ends, compression test performed with all 6 at 415 to 425 psi, turbo boost sensor checked and also replaced, voltage to ecm checked while running, wiring inspected on the engine sensor harness, blower bypass removed and checked for operation, inspection covers on side of block tight and no leaks, exhaust manifolds inspected for exhaust leaks, restricted fitting inspected for blockage, fuel return test in bucket showed no air and 1.1 g/m return @ 1200 rpm, fuel pressure is 65 at NL speed and 50 at idle, never been reprogrammed except by us, 1995 engine/truck, this is a recent purchase from New Jersey, customer needed a rebuilt fire engine and this was it, we cannot see any rebuild repairs on the repair sheets,
I have thought of 2 ideas since the holladay: try another ecm, check fuel presssure with the return line in a bucket-I am not happy with the fuel pressure at idle- that is why the restricted fitting removal/check,
When the turbo boost gets up to 6.4 " boost, the truck performs perfect.
Someone suggested exhaust back pressure but this would show up as increased turbo boost- not slow boost, I have 2 recorded test drives and whem the throttle is pushed to the floor the ecm logs 54% engine load then backs off to 44% and waits for the turbo boost to catch up to 6.4 lbs then allows the load % to increase to 100%. We also checked the Allison transmision for proper gear startup, it tested starting up in 1 then going thru the gears, I had thought of starting up in 2nd.

Any thoughts??? ??? ???

-------------------------
DDA tech for 30 years,all 2 cycle,series 60,50 mbe also.
1995 F250, 191k mi.
Lost Wages, Nv

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westcoast

Posts: 982
Joined: Dec 2008

Thursday December 25, 2008 21:12

G,day gonefishen , merry christmas from down under -- 50lbs fuel pressure at idle suggests to me that the regulator in the pump is stuck in the housing , as you already know that fuel pressure should be about 10 psi at idle , have you checked from the restrictor fitting back to the tank to make sure return fuel is actually getting back through the hose or is it pushing fuel through the tips until it can get enough air box pressure to use the fuel ? just one thought , is this unit intercooled as well as after cooled ? Have you checked torque convertor pressure to make sure the transmission s not loading up ? What about inlet and exhaust pressures ,I,ve had a similar problem with an 8V92 that had done a turbo hot wheel ,somebody replaced with new turbo but left the old hot wheel in exhaust system , it turned sideways and caused similar problems . Are the blower shaft and drive ok , Ive seen many slip with worn splines and still partially drive , is there any obstruction between turbo and after cooler ? Do we have good air box pressures ?. I,LL check t/row with you , when do you go back to work after the holidays ? regards David

-------------------------
detroit

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westcoast

Posts: 982
Joined: Dec 2008

Thursday December 25, 2008 21:24
G,day , just one thing I forgot - Does this fire tender just use the ddec control for shutdown ? because over here we have the old emergency shutdown flap as well, I,ve seen them with worn latches and flap springs causing a restriction. Regards David ------------------------- detroit

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stump

Posts: 814
Joined: Aug 2007

Friday December 26, 2008 06:39
Gonefishin have you checked the switch on the gas pedal,maby the signal is out of calibration?

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westcoast

Posts: 982
Joined: Dec 2008

Friday December 26, 2008 20:48

G,day gonefishen and stump, Excess fuel pressure is a mechanical problem , the pedal counts might be wrong but the fuel pressure problem will have to be fixed first , as you blokes know it can be a couple of things : ie regulator in pump , restricted R80 or hose to tank , a flap or bubble in pressure hoses or crossover hose between cylinder heads , incorrect size fuel hose after the secondary filter or just a partially blocked fitting in one of the cylinder heads , Gonefishen said that it was supposedly recon, but with no paperwork as to work done your at the mercy of somebody elses work .Has someone crossed fuel pipes on heads ;ie one heads getting cold fuel and the others getting hot fuel ? Regards David

-------------------------
detroit

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GoneFishen

Posts: 1325
Joined: Jan 2007

Friday December 26, 2008 22:28

Throttle counts at the ecm were checked, ohm resistance also checked at the foot pedal, DDEC engines 92 series in vehicles do NOT have cac, also there is no emergency shutdown flapper in use on theis unit, [seen them on the V8 versions], fuel line routing was verifyied by myself, R fitting was verifyied and no opstruction found there. Fuel pump pop off pressure is about right for this unit as the fuel pressure does not exceed 68 psi, The return line will be checked Monday day shift. There are no 92 people now at the shop just me and since I have been acquainted with them since the late 60"s , well you know. The fuel pressure is an issue, it starts at 55 at idle then drops to 44 psi. I am bothered by this. I finally got thru DDA today and programmed a test ecm. Monday will tell a bit more. I can stomp on the throttle now and get a wee bit of black smoke, about time for some of that. I think the pressure is a figure with this problem. I will keep everyone advised for our future reference. Damn, I hate it when I have to rely on others to do the work and testing. I would prefer to just do it myself sometimes. Things get tested faster and I can think as I work. Oh well I jhave all weekend to think.
Hope all had a merry Christmas, best wishes to all here in the New Year.

-------------------------
DDA tech for 30 years,all 2 cycle,series 60,50 mbe also.
1995 F250, 191k mi.
Lost Wages, Nv

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westcoast

Posts: 982
Joined: Dec 2008

Saturday December 27, 2008 18:59
G,day gonefishen , It,s always easier to do it yourself - I gather most of the tradies at your shop are 4 stroke trained ? I,m back at work t/row so I,II keep tabs on your progress Regards David ------------------------- detroit

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JoeZ

Posts: 938
Joined: Dec 2008

Saturday December 27, 2008 21:58

Generally if the restrictor is plugged or the return line is causing the problem, the engine will be slow to come down from high idle and will even stall sometimes. I do think you have a high fuel pressure problem though.

-------------------------
One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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GoneFishen

Posts: 1325
Joined: Jan 2007

Saturday December 27, 2008 23:50
JoeZ, we are about the same age if we have been in the business this long. I started in the late 60's. This is a DDEC engine so the engine will return as usual. I still am thinking abut the hot fuel thing/restricted fuel line. ------------------------- DDA tech for 30 years,all 2 cycle,series 60,50 mbe also. 1995 F250, 191k mi. Lost Wages, Nv

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JoeZ

Posts: 938
Joined: Dec 2008

Sunday December 28, 2008 02:38

I put a 500hp 8V92 DDEC in a motorhome where a manual control engine came out of. Bought it new from a local DD dealer who stocked them for E-ONE. It ran fine for about one day and the same problem you have showed up. After a day and a half of tracing my steps over and over, I finally checked fuel pressure. It was too high so I decided to take the line off the return and put it into a pail to see if it helped. At first fuel flowed freely, but after the first time I ran the engine up to high idle, the flow almost stopped completely. When I removed the restrictor (what a pain) it had a sliver of rubber in it. After I cleaned the restrictor, it has been running fine for the last ten years.

P/S I quit high school to do this in 1967....it has been rewarding and challenging to say the least.

-------------------------
One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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GoneFishen

Posts: 1325
Joined: Jan 2007

Sunday December 28, 2008 10:39
JoeZ, I graduated in 66. Close enough. ------------------------- DDA tech for 30 years,all 2 cycle,series 60,50 mbe also. 1995 F250, 191k mi. Lost Wages, Nv

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JoeZ

Posts: 938
Joined: Dec 2008

Sunday December 28, 2008 20:12

Yep...I would have graduated in 1967, but I goofed off too much. So you may have me by a a year. I'm just hoping I can make it for the next two years without any high dollar upgrading on equiptment. Us independent shops are falling by the wayside. You can't afford to keep up to date with business as slow as it is. Also, I have Cat, Cummins, Mack and Detroit within 10 miles from my shop, so I'm only able to offer Cummins and Allison warranty at this time.

-------------------------
One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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stump

Posts: 814
Joined: Aug 2007

Monday December 29, 2008 05:59
Joe Z and Gonefishin, the thing is that you 2 have forgotton more than most of these new tech's will ever know!!!

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JoeZ

Posts: 938
Joined: Dec 2008

Tuesday December 30, 2008 19:38

Thanks Stump....But I would have to say that GoneFishin has me beat by a mile on the more modern engines. I know the older ones like the back of my hand, and I can make it through the modern ones, but it doesn't come easy. Over the last 20 years the electronic technology has moved just a bit faster than I can keep up with. I'm still working on the engines from the stone ages....like the 6-110. Most mechanics never heard of them.

-------------------------
One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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