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Discussion Starter #1
Hello y'all new here to the forum and first time posting as well. I'm hoping somebody can help me with my situation or can give me a little insight. I have an 04.5 Dodge Ram 3500 6 speed with no start situation. At first, of course, when working would fire right up with no hesitation then within the last week I notice cranking time increased but would still start. This morning nothing, started with a little shot of ether and ran fine. Turned it off and tried to restart but nothing again. Shot a little bit more of ether and only started after cranking for a long time.

First basic things I did was replaced the fuel filter, lift pump and verified fuel delivery to my CP3 pump so I know low pressure side of fuel system is in good working order.

Now I'm stuck on my high pressure side which I suspect my CP3 is shot. I checked the PRV which was leaking a little so I blocked off with a bolt. Checked my fuel lines and all were tight. In doing so, I decide to crack cylinder #1 line to see if I was getting any fuel to the rail. I noticed my fuel rail was dry like CP3 wasn't putting any fuel out so I disconnected discharge line from the pump and fuel trickled out.

So here is video of how the flow is coming out of the discharge port on the CP3 which is suppose to go to the fuel rail. Also this is with the FCA disconnected so I would assume it should be gushing out. I don't know what you guys think?

 

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Any codes?
fuel in oil ?
What is rail psi?
Get a measuring cup and catch that fuel see
 

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Typically this situation is a bad injector not allowing the rail pressure to build. If you don’t have a rail pressure gauge you can tap into the rail
Pressure signal and measure it with a voltmeter. When I did this I got over 2 volts when cranking.

I had a no start which turned out to be the crank sensor

Chay
 

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Typically this situation is a bad injector not allowing the rail pressure to build. If you don’t have a rail pressure gauge you can tap into the rail
Pressure signal and measure it with a voltmeter. When I did this I got over 2 volts when cranking.

I had a no start which turned out to be the crank sensor

Chay
Few times I have seen bad crank or cam sensors and started with either because the either would spin the motor fast enough to somehow register.
 

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Discussion Starter #5
Thanks for the fast response guys. There are no codes and no fuel in the oil. As far as rail pressure, I dont know what it is at the moment so I will have to test for that. I had crank sensor installed last year but was getting a code for it. Put new one in and code went away. Haven't had issue since.

I will try to get fuel rail pressure today and keep posting updates
 

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Discussion Starter #6
Hey guys, I know its been a while but it has been very difficult to even do anything on my truck with long hours at work and then COVID-19. Anyways, here is an update with my truck and hopefully it can help someone experiencing same symptoms.

After I received a couple responses here I decided to double check everything.

First, I scanned for codes even though my check engine light wasn't on. I kept getting an engine code "P0251 CP3 pump regulator control" so I decided to get the FCA as I was able to snatch one from Ebay for $25 OEM Bosch. I installed it and truck didn't start nothing didn't even try, so I cracked Cyl # 1 fuel line again to see if I was getting fuel and now there was some fuel it wasn't dry like before. So after doing some more researching online I decided to do a volume test on the CP3 which surprisingly passed according to manufacturer. specs I got exactly 210 ml of fuel in my jar and engine code went away. So I ruled pump out as being a possible issue.

Next I decided to test for pressure at the rail. I know rail pressure needs to be at least 4000 psi in order for ECU to fire injectors. I didn't have a pressure gauge so I used the voltmeter way as suggested by Cfoss which I was getting 0.54 volts so I knew I was not building pressure, like an injector was leaking way too much fuel. So I decided to do best next thing and started to cap off one injector at a time while reading pressures. I unplugged the injector harness just to prevent truck starting. I began at #1 injector and worked my way up to #4 injector until I finally saw volts jump up to 1.08 volts, actually truck fired off for like a second. So I decided to button everything back up except #4 injector just capped off at rail and BAMM she fired off running just on 5 holes.

So now I ordered an injector and should be here tomorrow. I will let y'all know how it goes if I get time to install this week.
 

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I didn't have a pressure gauge so I used the voltmeter way as suggested by Cfoss
Can you elaborate on this to help any others who may be able to use this method.
 
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I may have this very same issue. I watched a utube video where the guy had a welded shut injector line he put on the fuel rail and sure enough the truck fired when he closed off #2 cylinder, ran like crap on 5 but it ran.
 

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Your call but all 6 injectors have seen same fuel/wear, being that a worn/leaky injector can easily damage engine all 6 injectors should be replaced.
Also NEW REAL Bosch or BBI will have updated design/material changes.
 

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I may have this very same issue. I watched a utube video where the guy had a welded shut injector line he put on the fuel rail and sure enough the truck fired when he closed off #2 cylinder, ran like crap on 5 but it ran.
Remember post # 7?
 

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2 Things raised my eye brows. $25 Ebay fca doesn't sound like a reliable fca. Most go for 120-150 That could be problems fast. If you have to do 1 injector you should do all 6. I know people run into money issues with buying 6 injectors and putting one in for a while can help, just food for thought.
 

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Ships from China, definitely not real. Cheap China knockoff. Their fakes are convincing on the outside.
 
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Remember post # 7?
SOMETIMES you do things the way you can...remember that.
 

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Discussion Starter #16
Can you elaborate on this to help any others who may be able to use this method.
Yeah its pretty easy to understand a pressure sensor and its usually a 0-5 volt circuit (actual range start at .5 volts and max out at 4.5 volts). Also its usually linear so it is easy to calculate pressures depending on voltage output. So in this situation I am assuming since I don't have actual specs of the pressure sensor but .5 volts is 0 psi and 4.5 volts is 30,000 psi, all I needed while performing my diag was to see an increase of voltage. As I capped off injectors there was no change maybe thousandths nothing significant but when I got to injector #4 voltage jumped to approximately 1 volt so that's like 5000 psi so right away it identified my bad injector, stuck open returning too much fuel. To verify, I also continued to cap off injector 5 and 6 and got same results as when I did 1,2 and 3.

I added a picture hopefully it can clear some stuff where I back probed exactly.
 

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Discussion Starter #17
Also guys I appreciate the feedback about buying all new injectors but its too expensive to replace all injectors at once when its just # 4 that crapped out on me. Im taking my chances on just replacing that one injector and will let yall know how it holds up. Also the FCA I got from Ebay shipped from Trenton, NJ packaging was legit, stamping and quality was same as my original FCA so there are some places that sell OEM at a cheaper price, just got to look.
 

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Thank you for posting that.
 

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👍👌
 
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