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Old 10-17-2020, 09:50 AM   #29
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It sounds like a fuel pump relay is going out I've had this a couple times it'll test good but it'll drop out in mid cycle or just will not engage at times it won't connect and work like it's supposed to I would install a new fuel pump relay and try it for a while
This is easy to test if the problem reoccurs often remove the plastic cover on the relay and when it won't start you don't have fuel pressure without shutting the key off or anything bypass the relay with the jumper wire or push on a little contact with your finger if the fuel pump runs at that time then you know your problem is electrical in the relay area
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Old 10-17-2020, 07:15 PM   #30
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Quote:
Originally Posted by Roy-c View Post
Quick question. Have you looked at a wiring schematic for the fuel gauge sending unit ? that will tell you what color and how many wires are there and if there are wires that power an in tank fuel pump which is ALWAYS part of the sending unit assembly. ( If your repair shop couldn't tell you if you have an in tank pump you need to find a new shop.
Don't have a schematic, either configuration will have wiring going to a sending unit and a pump, that won't tell me anything.
Shop was going to drop the tank, at about 4 hours labor, they advised against since they were not able to get it to not start in almost a week sitting there. I agreed and took it home, as I previously stated, I put it up in the air and searched the entire frame rails on both sides and could not find a pump, and as I stated, the frame and tank are so tight, it's impossible to get your hands inside or on top.
Just waiting for someone that has actually dropped the tank on one of these to chime in. Everybody has ideas and opinions, but unless you actually dropped the tank on one of these you don't know. I may be the guy to drop it if the problem re-appears. Then I will know for sure.
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Old 10-17-2020, 07:20 PM   #31
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Quote:
Originally Posted by Brad247 View Post
It sounds like a fuel pump relay is going out I've had this a couple times it'll test good but it'll drop out in mid cycle or just will not engage at times it won't connect and work like it's supposed to I would install a new fuel pump relay and try it for a while
This is easy to test if the problem reoccurs often remove the plastic cover on the relay and when it won't start you don't have fuel pressure without shutting the key off or anything bypass the relay with the jumper wire or push on a little contact with your finger if the fuel pump runs at that time then you know your problem is electrical in the relay area
As stated earlier, relay has been changed to a new Omron relay, actually changed twice, these are industrial quality relay's, I have used hundreds of them building industrial machines.
Problem still appeared with both relays, and I made sure they were seated properly.
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Old 10-18-2020, 02:38 AM   #32
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Look for an oll pressure switch controlling the fuel pump.
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Old 10-18-2020, 07:07 AM   #33
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Originally Posted by twinboat View Post
Look for an oll pressure switch controlling the fuel pump.
Don't think GM did that on these. I have driven this rv from NY to FL several times, and it never died once it's running, there has been maybe 4 times that it started after sitting and died as if running out of fuel in a few seconds, because of no fuel prime. That's why I replaced the fuel relay and ignition switch, still the same, I'm thinking it's possibly in the ECU that sends the prime signal when the key is first turned on.
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Old 10-18-2020, 07:44 AM   #34
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Sorry I thought you just tested relay didn't know you replaced it I would still pull the plastic cover off of the relay and when the problem happens again don't turn the key off and go out and manually push the relay that will help diagnose to where the location of the problem is it could be control circuit for the relay with that said you would have no reason to drop the tank and change a pump out
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Old 10-18-2020, 08:04 AM   #35
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Sorry I thought you just tested relay didn't know you replaced it I would still pull the plastic cover off of the relay and when the problem happens again don't turn the key off and go out and manually push the relay that will help diagnose to where the location of the problem is it could be control circuit for the relay with that said you would have no reason to drop the tank and change a pump out
I did try wiggling the relay one time when it would not start, and nothing worked, I left the key on and wiggled it around, removed and reseated it, and actually swapped it with the horn relay that's next to it and the same relay, and pump did not turn on because I believe it only receives the prime signal for a second or so and then after it starts and the cps tells it the engine is running then the fuel pump gets a signal to run. I had to cycle the key off and then back on for the relay to pull in and start the pump. When I swapped out the relays and tested with the horn it worked every time. I still believe this is something in the ECU randomly not sending the prime signal when the key is first turned on. RV has new batteries and Alt works normal, always shows about 14 volts when running.
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Old 10-18-2020, 08:22 AM   #36
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We just purchased an RV on Friday. It would not start after having run a few minutes earlier. Replaced crank position sensor and it now runs like a champ.
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Old 10-18-2020, 08:32 AM   #37
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We just purchased an RV on Friday. It would not start after having run a few minutes earlier. Replaced crank position sensor and it now runs like a champ.
I was thinking of changing that but the shop I had it at said if the cps fails or is about to fail and acts up it throws a fault code and trips the check engine light, even if it does actually start. Did yours throw a code?
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Old 10-18-2020, 08:52 AM   #38
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Gas RV cranks but won't start

Quote:
Originally Posted by sneaky View Post
Don't have a schematic, either configuration will have wiring going to a sending unit and a pump, that won't tell me anything.

Shop was going to drop the tank, at about 4 hours labor, they advised against since they were not able to get it to not start in almost a week sitting there. I agreed and took it home, as I previously stated, I put it up in the air and searched the entire frame rails on both sides and could not find a pump, and as I stated, the frame and tank are so tight, it's impossible to get your hands inside or on top.

Just waiting for someone that has actually dropped the tank on one of these to chime in. Everybody has ideas and opinions, but unless you actually dropped the tank on one of these you don't know. I may be the guy to drop it if the problem re-appears. Then I will know for sure.


Unless something is different on a 5500 motorhome chassis, The inline fuel pump you see in the parts catalogs only acts as a transfer pump between the primary and secondary fuel tank on a 5500 series truck chassis. Had a flatbed I used for snow plowing that would not run off the secondary tank and I found there was defective inline pump between the tanks.

Next time it wonít start, perhaps you should pull the engine cover and hook up your timing light to make sure you arenít chasing the wrong demon.
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Old 10-18-2020, 09:03 AM   #39
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Originally Posted by RickNC View Post
Unless something is different on a 5500 motorhome chassis, The inline fuel pump you see in the parts catalogs only acts as a transfer pump between the primary and secondary fuel tank on a 5500 series truck chassis. Had a flatbed I used for snow plowing that would not run off the secondary tank and I found there was defective inline pump between the tanks.

Next time it wonít start, perhaps you should pull the engine cover and hook up your timing light to make sure you arenít chasing the wrong demon.
Good point about the fuel pump. I did see mention in the parts listing that for that chassis there was a 55 gal and I think a 28 gallon tank combination, so maybe that pump they are showing is actually a transfer pump, would make sense. But,... Can't find any listing for an in tank assembly for a 2004/5 C5500 80 gallon gas chassis???.
That's why I'm hoping someone that actually dropped the tank from a C5500 RV will chime in.
Is the tach supposed to show rpm when the engine is cranking?, Mine does not till it starts??
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Old 10-18-2020, 10:33 AM   #40
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Quote:
Originally Posted by sneaky View Post
Good point about the fuel pump. I did see mention in the parts listing that for that chassis there was a 55 gal and I think a 28 gallon tank combination, so maybe that pump they are showing is actually a transfer pump, would make sense. But,... Can't find any listing for an in tank assembly for a 2004/5 C5500 80 gallon gas chassis???.

That's why I'm hoping someone that actually dropped the tank from a C5500 RV will chime in.

Is the tach supposed to show rpm when the engine is cranking?, Mine does not till it starts??


I have never paid attention to the tachometer while starting so I cannot say whether it moves or not.

FWIW, On my 1995 w/ 454 I can reach around the heat shield on the passenger side to hook the timing light on #6 plug wire (opposite cylinder of #1) to check timing. Lot quicker than removing the engine cover on my rig.
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Old 10-18-2020, 02:26 PM   #41
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The Kodia chassis has a tilt front end like a semi so it's super easy to get to the plug wires. I'll try that and then I'll know if it's a fuel or ignition issue
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Old 10-19-2020, 08:19 AM   #42
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You are correct it only receives a prime signal for a very short time but if the covers off the relay and you can manually trip the relay and it works that will tell you if you have a problem with your fuel pump or a problem with your signal coming into the relay
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