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Old 08-30-2016, 12:07 PM   #1
Almost There
 
Join Date: Sep 2015
Location: Salt Lake City, Ut
Posts: 82
Year: 98
Coachwork: Thomas
Chassis: D
Engine: 7.2L turbo Cat C7 3126
Rated Cap: 84
Reading 98 Thomas MVP Cat C7 fault codes

Hello,
Does anyone know how to read the fault codes on a 98 Thomas MVP ER with a Caterpillar Acert C7 engine?

I found several links on how to do it on later models, (like this one: http://www.carolinathomas.com/wp-con...mas-Bus-70.pdf) but my dash doesn't look like the one shown. I don't have cruise control, or a mode/reset button.

The check engine light is not currently on, but the engine won't start so I suspect there is a code being stored somewhere. Thanks!
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Old 08-30-2016, 05:36 PM   #2
Bus Crazy
 
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,188
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
Is there a J1587 data link connector under the dash? It may be that you have to find diagnostic tools to scan for codes, rather than reading them out on the dash. J1939 is another option, but that PDF you linked suggests Thomas didn't start using J1939 until 2010. The PDF also mentions "ICU3 and ICU4 dash models." Maybe yours doesn't have that model of dash and so doesn't work as described in that doc.

If I remember correctly you were/are in Salt Lake City. I could refer you to a shop if you're still in the area.

You didn't really ask "help me figure out why my engine won't start" ... but I'll ask anyway: does the engine crank but not run, or does it not even crank when you turn the key to the start position?
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Old 08-31-2016, 08:50 AM   #3
Almost There
 
Join Date: Sep 2015
Location: Salt Lake City, Ut
Posts: 82
Year: 98
Coachwork: Thomas
Chassis: D
Engine: 7.2L turbo Cat C7 3126
Rated Cap: 84
Thanks for your help family wagon! There is a diagnostic connector under the dash, but I am not sure what kind it is. It looks like a 12 pin ALDL connector, but the pinout appears non standard. The pins are labled A-M but only A, H, J, and K have wires in them (A = Black, H = Yellow, J = White, K = Blue) The connector itself has a cap that says "diagnostic connector" which was helpful. Inside the cap, there are two metal prongs which look like they would connect Pins L and M together (if there was a wire going to pin L).



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Old 08-31-2016, 09:27 AM   #4
Almost There
 
Join Date: Sep 2015
Location: Salt Lake City, Ut
Posts: 82
Year: 98
Coachwork: Thomas
Chassis: D
Engine: 7.2L turbo Cat C7 3126
Rated Cap: 84
The engine suddenly won't start and I have no idea why. It was running fine for several months. In the beginning of August, I drove it from Dallas to Salt Lake (1200 miles). I replaced both fuel filters about 1500 miles ago. Before the big trip I replaced the oil, replaced the belts, topped off all the fluids. The bus ran really well during the trip. 3 weeks later I go to start the bus and it won't start. The starter is engaging, the engine is turning over, but no ignition. I have 6 parallel batteries on the bus (2 normal lead-acid and 4 marine deep cycle) and they are all fully charged. I have a hand pump on the fuel line, so I don't think there is air in the fuel line. The tank is half full and I'm parked relatively flat. The check engine light is not on. I was hoping to connect a diagnostic tool in and see if that would point me in the right direction. When I checked the oil yesterday, it was quite low and I had just filled it up prior to the trip so I need to look into that. I have the 22 quart pan and I was about 4 quarts low. The engine exhaust was clear, so perhaps I am leaking oil, not burning it. Also, when use the hand fuel pump, I can hear a slight hissing coming from the far end of the engine. I do not know if that is normal air being vented, or if there is a o-ring injector leak, or something else.

98 Thomas ER MVP
Cat C7 model 3126
113K miles

I would love a shop recommendation or any other suggestions on what to try next. Thanks!
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Old 08-31-2016, 01:51 PM   #5
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 6,080
Year: 1991
Coachwork: Carpenter
Chassis: International S3800
Engine: DT360
Rated Cap: 7 Row Handicap
sounds like you asre getting air in the fuel lines somewhere.. is your electric fuel pump a lift pump back at the tank or is it up front and sucks the fuel from the tank and thriough the filters?..

-Christopher
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Old 08-31-2016, 02:11 PM   #6
Skoolie
 
Join Date: Aug 2016
Posts: 115
I do not know a lot about it, but on my van wouldn't crank so I did what Family Wagon said and bought a diagnostic tool and found out through the codes it would not crank because of a fuel fuse, so I switched them around and it cranked and been running every since. In the manual it tells you how to read the codes.
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Old 08-31-2016, 03:02 PM   #7
Bus Crazy
 
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,188
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
Hmmm. I don't recognize that diagnostic connector. The J1708 is the style mine has; it's a round connector with (I think) 9 pins but only 4 or so populated. The newer J1939 is also round so far as I know, and then of course there's the D-shape OBDII as well. But yours doesn't resemble any of those.

In case you want a Thomas dealer, Lewis Bus Group is their dealer here in the Salt Lake City area. About a year ago they moved up near the north end of the I-215 belt route. Their phone is (801) 364-4219. I'll send you a PM with a little more info as well.
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Old 08-31-2016, 05:09 PM   #8
Almost There
 
Join Date: Sep 2015
Location: Salt Lake City, Ut
Posts: 82
Year: 98
Coachwork: Thomas
Chassis: D
Engine: 7.2L turbo Cat C7 3126
Rated Cap: 84
I found another diagnostic connector in the fuse box on the front drivers side. It is a J1708, round 6 pin connector. I used an ohm meter and found that the J1708 connector is tied to the ALDL connector.

Wiring Connections
ALDL Signal J1708
A Ground E
H Battery C
J J1708+ A
K J1708- B

As I understand it, J1708 just specifies the physical layer, does anyone know what protocol the engine uses to communicate through this port? Or does anyone know what diagnostic tool I should buy/borrow/rent to read the engine codes?
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Old 08-31-2016, 05:13 PM   #9
Almost There
 
Join Date: Sep 2015
Location: Salt Lake City, Ut
Posts: 82
Year: 98
Coachwork: Thomas
Chassis: D
Engine: 7.2L turbo Cat C7 3126
Rated Cap: 84
I was reading on the forum that a common problem on C7 engines is an injector seal leak. Someone said that this would cause oil to return to the fuel tank. I unplugged the tank drain and captured a quart or two of fuel, but it looks like normal diesel, so maybe the problem is fuel pump or ECM related.

I do not believe that there is a lower fuel pump, the HIEU sucks fuel up. This is why the manual fuel pump is so useful to prime the system.

Does the HIEU pump have a fuse I could check?
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Old 08-31-2016, 05:49 PM   #10
Bus Crazy
 
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,188
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
I played briefly with a Chinese heavy truck scan tool but sent it back because it turned out the thing was pirate-ware through and through. It was a clone of the Nexiq USB Link and included DVDs with cracked installers for the diagnostic software for just about all the names in heavy trucking (Cummins, CAT, Allison, Bendix, Perkins, and so on). I wish this stuff could be had legitimately for even $500-ish instead of the thousand(s) the real deal currently sells for. A word of warning to anybody who might decide to seek out the Chinese pirated versions: Set it up on a dedicated computer and keep it away from your good computer. Cracked software is often also virus-laden.

As for legit heavy truck scan tools: there are some all-in-one setups priced at $1000-$2000. There are also computer link cables like the Nexiq USB Link I mentioned earlier. I think I found it about $600, but then there's hundreds to thousand-and-some dollars of additional cost for the software from the various manufacturers. It gets spendy fast.

Right, J1708 is just physical (RS-485 and a round connector more or less). SAE J1587 defines the protocol on top. I haven't coughed up the money to buy a copy of that spec yet. Though I did acquire a copy of the American Trucking Associations Technology & Maintenance Council RP1210 spec.. I found a legit but dated CD version of the TMC manual containing RP1210 from maybe year 2010 on Amazon for about $30. I hoped to build something similar to the Nexiq data link hardware but that project hasn't gone anywhere.
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