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Poor running, now no start after fuel filters changed
#1

I changed the two fuel filters, one at a time and on the 8V92TA Detroit  and filled them with diese before installing them. This is the 8th time in eight years that I have done this with no problems. Well the 9th time is an issue. Strarted the coach up. Ran for about 30 seconds perfectly, no leaks. Then it started running rough, like 1 cylinder was not contributing.  I was unable to raisse the rpm's and shut the motor down. Removed the first filter, looking for perhaps a double gasket situation, but all was good. Same with the 2nd filter. Replaced them one at a time with spare filters, filling the filters with diesel. Now the coach is still a no start. Never had to purge air. I don'tknow how to proceed. Iam avoiding cranking for long periods, trying to avoid damaging the starter with heat. Any suggestions?

Guy & Sue Cobham
Sioux Falls, South Dakota
1984 Classic 40' #59
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#2

(03-21-2026, 04:30 PM)Guy Wrote:  I changed the two fuel filters, one at a time and on the 8V92TA Detroit  and filled them with diese before installing them. This is the 8th time in eight years that I have done this with no problems. Well the 9th time is an issue. Strarted the coach up. Ran for about 30 seconds perfectly, no leaks. Then it started running rough, like 1 cylinder was not contributing.  I was unable to raisse the rpm's and shut the motor down. Removed the first filter, looking for perhaps a double gasket situation, but all was good. Same with the 2nd filter. Replaced them one at a time with spare filters, filling the filters with diesel. Now the coach is still a no start. Never had to purge air. I don'tknow how to proceed. Iam avoiding cranking for long periods, trying to avoid damaging the starter with heat. Any suggestions?

Not sure if your bus has the hand primer pump on the fuel tank, but if it does you could try pumping that. Some Newell's have a primer on the fuel filter housing, should look like a black button. 

One other thing that I like to do is always start and run the engine for a few minutes before you change fuel filters. This gets the engine hot and makes it easier to start since you are not fighting a cold start on top of air in the fuel. 

My way to get the air out is to use my milwaukee vacuum with the hose on the blow side and I put it into the fuel tank with a rag wrapped around it. It does not have to be a perfect seal and there is a vent on the tank so some of the air is going to go out the vent on the tank. I usually do this with two people so one can hold the vacuum hose on the tank and then you can unscrew one of the fuel filters until fuel starts to come out of it. Once you have fuel coming out the filter put it on tight and let the vacuum continue to run. I usually try to start it while I still have the vacuum blowing into the fuel tank to try to get the fuel into the fuel pump. Detroit fuel pumps are very hard to prime when there is air in them, they do not pull air hardly at all.

Another note I will mention, if this is on the 84 Newell you may want to look into replacing fuel lines if you have not already. The fuel lines could be sucking air and not helping the situation. They hoses tend to not leak fuel but can suck air so its often overlooked.

Jeff LoGiudice
Temple Terrace, Fl & Loudon & Monterey, TN
1984 Bluebird Wanderlodge PT40
1998 Newell 2000 #490
1986 MCI/TMC 102A3 (sold)
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#3

Use the primer and the mechanics start switch in the rear of the coach. Prime till the bulb is to tough to push then hit the starter. Might take multiple tries. Keep going till it works. I just changed mine and had to do that for about 30 minutes. Finally got it primed and running.

Carl Little
1996 Coach 435 Detroit 60
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#4

(03-21-2026, 05:41 PM)cwl1979 Wrote:  Use the primer and the mechanics start switch in the rear of the coach. Prime till the bulb is to tough to push then hit the starter. Might take multiple tries. Keep going till it works. I just changed mine and had to do that for about 30 minutes. Finally got it primed and running.

(03-21-2026, 06:54 PM)Guy Wrote:  
(03-21-2026, 05:41 PM)cwl1979 Wrote:  Use the primer and the mechanics start switch in the rear of the coach. Prime till the bulb is to tough to push then hit the starter. Might take multiple tries. Keep going till it works. I just changed mine and had to do that for about 30 minutes. Finally got it primed and running.

I will look for a primer bulb. i have never seen one before, but perhaps i missed it. Thanks !

Guy & Sue Cobham
Sioux Falls, South Dakota
1984 Classic 40' #59
Reply
#5

Mine is a black button looking thing right on top of the fuel water separator.

Carl Little
1996 Coach 435 Detroit 60
Reply
#6

If you have the primer on the fuel filter it will probably look like this:
   

Jeff LoGiudice
Temple Terrace, Fl & Loudon & Monterey, TN
1984 Bluebird Wanderlodge PT40
1998 Newell 2000 #490
1986 MCI/TMC 102A3 (sold)
Reply
#7

            Thanks for all the suggestions. Here is what I am dealing with. The fuel water seperator is a very obsolete one designed for the genny and the 8V92TA. It is mid coach nest to the fuel tanks. The engine bay has a primary and secondary fuel filter. Earlier today we applied posittive air pressure to the puel taks with a rag and reversed shop vac, Got  little white and then a puff of black smoke, but no fire. Only did it for 30 second intervals. Then waited 10 minutes between tries. Didn't want to overheat the starter.

Guy & Sue Cobham
Sioux Falls, South Dakota
1984 Classic 40' #59
Reply
#8

Are you actually in south dakota. How old is the fuel? Is your coach outside? Or in a cold storage place? I won't lie. I gelled mine this winter. I last got fuel in mid September in new york state. Being parked outside through the cold it didn't stand a chance. I had to wait for a week above 34 and then swap filters and reprime and add fresh winter fuel to get it going again. Of course I also had to pull it out of the soft yard through the mud yesterday. And today its snowing again... figures.

Carl Little
1996 Coach 435 Detroit 60
Reply
#9

(03-22-2026, 01:45 PM)Guy Wrote:  Thanks for all the suggestions. Here is what I am dealing with. The fuel water seperator is a very obsolete one designed for the genny and the 8V92TA. It is mid coach nest to the fuel tanks. The engine bay has a primary and secondary fuel filter. Earlier today we applied posittive air pressure to the puel taks with a rag and reversed shop vac, Got  little white and then a puff of black smoke, but no fire. Only did it for 30 second intervals. Then waited 10 minutes between tries. Didn't want to overheat the starter.

In your photo it appears there is possibly a fuel pump and a switch (circled in red)? Do you know what those are for? Maybe they are there to prime the fuel system?


Attached Files Thumbnail(s)
   

Jeff LoGiudice
Temple Terrace, Fl & Loudon & Monterey, TN
1984 Bluebird Wanderlodge PT40
1998 Newell 2000 #490
1986 MCI/TMC 102A3 (sold)
Reply
#10

Good eye. I have never used it, but it marked on the dash. Wouldn't be the first thing mislabeled by one of the previous owners. I'll try it. What do I have to lose?

Guy & Sue Cobham
Sioux Falls, South Dakota
1984 Classic 40' #59
Reply


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