1991 Marquis - CAT 3176 - Engine Starting Problems

[Douglas Irvine]

Hi All, first post here looking for some troubleshooting help!

Since we got our Marquis about 2019 (Cat 31776 S/N 2YG03009) with 80k miles on her, she has intermittently had hard times starting. I followed the manual instructions, turning the ingntion key for ~ 30 secs (sometimes multiple times) to allow the fuel pump to prime the engine before trying to crank. The starter/batteries are great and always crank great. but sometimes the engine doesn't catch at all. Last summer she did this and would not start at all, no matter the rest I gave in-between tries. Of course we were in Thermopolis, WY with no real diesel mechanic let alone CAT knowledge. But some nice local mechanics and I dug through the manuals, and as a Hail Mary I tried pushing the "Engine Protection Override" momentary switch and held it while starting. She fired right up. Now every time I start her I hold that for about 10 seconds after the engine has caught and started idling and everything is A-OK. So I think that may point us in the direction of some sensor involved in the Engine Protection Override may be flaking out on me.

Other points to note: The tachometer doesn't kick up till the engine is idling for 10-20 seconds. The coolant level alarm has occasionally (1-2x a year) gone off with a false positive.

Googling around I wonder if I should be replacing: Coolant sensor(s)? Engine RPM sensor?

I haven't found any mechanics in Casper WY I'd trust with this baby. Maybe I'm just too mistrusting =-)

Looking for any guidance on where to start, as the co-pilot is seriously curtailing any RV'ing till I get this figured out!

Thanks in advance!

[Joel Ashley]

I'm sorry no one has yet responded to your request for help, Doug.  We aren't all ignoring you, but like me most may not be familiar with your coach chassis or with Casper.   I initially thought your ignition solenoid was the culprit, a common starting one, but since your engine cranks that isn't likely.  More so is a fuel delivery or, as you suspect, a sensor issue;  not my area of expertise for sure;  and I've not heard of an "Engine Protection Overide" switch. 

But the repair services guide that the Club maintains does list one Casper area facility that a Club member had positive results from: Wyoming Machinery:
https://www.wyomingcat.com/company-locations/casper/

You can find the RV Service Providers guide within the Members Only section on the Forum's Home page.

This person's was an experience from several years ago, and especially since Covid, as you know many companies have changed.  But it may be worth a call/visit.  I wish I could be of more assistance myself, but can only hope that between that link and another more experienced member's reply, you get this annoying problem resolved.

-Joel

[Douglas Irvine]

Thanks Joel! Yeah I am hoping some of the vintage coach folks on here will see this eventually, or maybe Dave A. Unfortunately, I heard CAT shops have stopped servicing motorhomes. I get my parts and filters from Wyoming Machinery Co. Maybe I should call them and confirm if they have followed the national trend of CAT shops.

[Steve Huber]

Douglas,
All (to best of my knowledge) CAT outlets stopped servicing "over the road" engines in about 2023. They built their last OTR engine in the 2008 or so. If diesel shops have the CAT engine analyzer they should be able to track down any sensor of other issue that logs into the engine control unit.
The Engine Protection Override allows operators to temporarily bypass automatic engine shutdown systems caused by low oil pressure or high coolant temperature. So you are getting an error signal from one of those 2 sensors.
I think the tach problem is either a bad connection at the alternator or in the wiring from the alternator to the ECU and then to the tach. The other possibility is a faulty tach.
In case you haven't found it there is a wealth of knowledge (diagrams, manuals, schematics, etc covering 84-94 Beavers on Coach Assist. To access it log in on the Club website, select Technical, then Coach Assist. Then Factory Brochures. Then click on the 3 bars in the upper left of the screen. Select Beaver Coaches 1968-1994 and then Schematics.
Steve