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Topic: 6V92 limp mode? (Read 705 times) previous topic - next topic

6V92 limp mode?

Hello Fellow Foretravelers. My 1989 U300 with a 6V92 is kicking my ass. The engine starts but seems to be in limp mode. Idles a little rough and revs sluggishly. I check for low coolant checked the fuel water separator for water (wasn't any) changed the secondary filter with no success.

I did some welding on the coach as I have done before. I disconnected the alternator, chassis batteries, and house batteries before welding. This has never been a problem in the past.

Any thoughts?

Thanks  Andy
Andy 1989 U300 40'

Re: 6V92 limp mode?

Reply #1 –
Limp mode is usually because of a sensor returning low coolant, low voltage, or other fault codes to the ECU. Flip the engine code switch under the dash and count the light bulb flashes. Compare that to the DDEC II fault codes on the attached PDF.

DETROIT DIESEL Electronic Controls DDEC-II Diagnostic Codes - Wanderlodge...

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: 6V92 limp mode?

Reply #2 –
An air leak in the diesel supply hose from the tank can also duplicate your symptoms. Does it idle at 600 rpm smoothly?

P
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: 6V92 limp mode?

Reply #3 –
Check ECM fuses if you blew one of  the fuses it will only run on 3 cylinders
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: 6V92 limp mode?

Reply #4 –
Andy,

Any smoke or stalling after start-up?  Like Pierce says absent a fuel or air restriction the codes will point us in the right direction.

Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: 6V92 limp mode?

Reply #5 –
Quote from: stump –
Check ECM fuses if you blew one of  the fuses it will only run on 3 cylinders
Interesting, I didn't know that.

I believe the fuses are located on the 12 volt panel in the bays (mine is in the utility bay, drivers side, forward wall).
According to the schematic there are 3 fuses (5 amp and two 20 amps).  Pic has a rectangle drawn around them.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: 6V92 limp mode?

Reply #6 –
I love all you folks! I'll dig in again with this new wisdom and let ya know.

As always thank you for taking the time to help out!
Andy 1989 U300 40'

Re: 6V92 limp mode?

Reply #7 –
Im going to name my next dog John Fitz! When I took the battery box cover off I must have hit one of the fuse holders and knocked the fuse out. It would have taken me a week to figure that out!!

I'm giddy!

Thank you all again!
Andy 1989 U300 40'

Re: 6V92 limp mode?

Reply #8 –
Glad to hear that.
Stump is your hero.  I would have never figured the ECM was split like that.  Now I'm wondering what that 3rd fuse does.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: 6V92 limp mode?

Reply #9 –
The 5 amp fuse powers off the ign key,it powers the circuit for cruise etc. The 2 20amp Fuses are the main ECM power supply fuses.  each fuse powers each bank independently.
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: 6V92 limp mode?

Reply #10 –
Right! A hearty thank you Stump!
Andy 1989 U300 40'

Re: 6V92 limp mode?

Reply #11 –
Here is a DDEC II wireing diagram.You can see snd follow the 5 amp fuse circuit.
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit