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Discussion Starter · #1 ·
Just bought my 01 about a month ago. Was having a hot start issue, took it into a shop and they said injection pump bad. I'm hoping they were just assuming and wanted my money, I just installed my new mechanical Isspro FP gauge tonight and went for a cruz to see where I'm at. And to help further diagnose before a drop a couple G. When I say a couple is because if I get a new IP I'm getting a new LP seeing as how mine is stock replacement about a year ago.
I mounted the gauge on the filter inlet via tapped banjo bolt and needle valve.
Here is what I'm seeing;
Bump the started it hits 21psi, idle its about 19psi, driving normal is about 14-15psi and pedal to the metal drops to about 9-10 psi. This seems like an abnormally large range. To me seems like Bad LP but hot start issue is more of a IP issue. What are your thoughts? Help me out please!

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Seems like very good pressure to me, i run about 30psi at idle and about 20 something at wot but i have a adjustable lift pump i would say the injection pump is fine, you have a pic of where u tapped for fp?
 

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Discussion Starter · #3 ·
I dont have a pic. It's on the line coming from LP to filter housing


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An 11+psi differential between idle and WOT fuel pressure is a strong indication the the lift pump is unable to keep up with the fueling demands.

IF the VP44 has seen insufficient fuel pressure as a result of a weak lift pump, then damage may have been done- a symptom of which could be hard starts...
 

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Not bad for a stock LP. Actually kinda high really. How long has it been since you installed the FP gauge? Sometimes entrapped air can give weird readings and take a day or two to work out of the system. How many miles on the VP? Why was the LP replaced? Exactly what is it doing for you to call it a hot start? Also, fill out your signature to better help you.:thumbsup:
 

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I dont have a pic. It's on the line coming from LP to filter housing


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If you're taking the pressure reading pre-filter, then you have no idea what pressure the VP44 is seeing. Could be far less, especially if the fuel filter is dirty...
 

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Discussion Starter · #7 ·
Just replaced the fuel filter. Sorry I'm not sure how to fill out my sig on my
Phone. The truck has 80k miles on it. Not sure the reason lift pump was replaced just know it was by previous owner about 10k miles and a year and a half ago. When I say hot start, it fires up without fail every time but once driven for a while and warmed up and takes a while of cranking for it to start. Runs perfect otherwise no rough idle or white smoke or anything . It also doesn't do the hot start all the time.


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Discussion Starter · #8 ·
So should I wait for air to work out or somehow bleed it or something before I jump to any conclusions? I the needle valve wasn't open enough could it cuz the pressure reading to drop. Just brainstorming here.


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Discussion Starter · #9 ·
One more thing i noticed is when it primes when you turn the key on it hits about 7psi and slowly bleeds off when I bump the starter it goes to 21 and slowly bleeds off. When i say slow I'm talking 1-3 min for it to go back to 0. I was watching moparman's video on how to adjust needle valve and his bleeds right back off....



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He is also taped at the pump not the filter , and he has the big line kit and a airdog
 

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Discussion Starter · #11 ·
He is also taped at the pump not the filter , and he has the big line kit and a airdog
Ahhh that's probably why then!


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If your hot hard start issue only happens when the engine is hot (fully warmed up) and its also hot outside then it could be that the VP's computer is giving signs of failure or..........even though its very rare to happen with an OEM lift pump, your lift pump could be placing to much pressure while the engine is cranking. The only way to tell if the later is the case is to unhook the LP and then try to start the truck. Unfortunately there isnt an easy way for you to disconnect the lift pump like others with aftermarket fuel pumps can but point is that, when you're experiencing this hot start issue, if you unhook the fuel pump and the truck starts like normal then thats your problem. Again, it is very rare for this to be an issue with OEM lift pumps but it obviously was common enough for Dodge to implement an ECM flash which disables the lift pump during engine cranking. I only say this because most OEM lift pumps dont put out such high pressure like yours does. OEM lift pumps usually supply around 15-16 psi at the most. But as I mentioned, the only way for you to know is to unhook the LP when its hot hard starting and the only way for you to do that is to unhook the connector down by the LP. Pain in the butt.
Lastly, if you do try this and it does start normal then just make sure you quickly turn the truck off and reconnect the lift pump before you drive away.:thumbsup:
 

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Discussion Starter · #13 ·
Does dodge charge to reflash? Is it something they can do in vehicle? And would I need to take out my edge ez? I'll try it the next time it does it to disconnect LP. It's tough now that temps are getting into the 40-50 for the high here in Utah. If the re-flash wasn't super expensive I would just go get it done anyways


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Does dodge charge to reflash? Is it something they can do in vehicle? And would I need to take out my edge ez? I'll try it the next time it does it to disconnect LP. It's tough now that temps are getting into the 40-50 for the high here in Utah. If the re-flash wasn't super expensive I would just go get it done anyways


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By saying what the temps are and it still hard hot starts, I'm leaning towards the fuel pump being the issue. If this only happened in hot summer heat then I'd possibly think the VP's computer. But if you're going to try unplugging the lift pump then you'll know for sure.

The dealer may or may not charge plus they possibly may not even know of the re-flash at all. All dealers aren't nice or smart or both. Some guys (like me) wont let the dealer touch my ECM since I've heard of too many guys say their truck runs poorly after a dealer re-flash. If you know someone with a Smarty then the Smarty can do the same thing.:thumbsup:
 

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Discussion Starter · #15 ·
By saying what the temps are and it still hard hot starts, I'm leaning towards the fuel pump being the issue. If this only happened in hot summer heat then I'd possibly think the VP's computer. But if you're going to try unplugging the lift pump then you'll know for sure.

The dealer may or may not charge plus they possibly may not even know of the re-flash at all. All dealers aren't nice or smart or both. Some guys (like me) wont let the dealer touch my ECM since I've heard of too many guys say their truck runs poorly after a dealer re-flash. If you know someone with a Smarty then the Smarty can do the same thing.:thumbsup:
Ok it did it when I drove to the store today. Unplugged the LP and it fired right up. Instead of a re-flash how about that relay that does the same thing? I also hate dealers I don't trust them!




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Ok it did it when I drove to the store today. Unplugged the LP and it fired right up. Instead of a re-flash how about that relay that does the same thing? I also hate dealers I don't trust them!
Awesome. I'm glad it worked. Are you good with automotive wiring? If so then you will easily be able to copy this relay diagram which will solve your hot hard start problem and save you lots of money. You can thank Moparman for the diagram too since he came up with that years ago.:thumbsup:

 

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Discussion Starter · #17 ·
I'm pretty good with mechanical stuff and following instructions but I don't quite understand the diagram, is there a write up in this anywhere I could follow? Thanks for all the help


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I'm pretty good with mechanical stuff and following instructions but I don't quite understand the diagram, is there a write up in this anywhere I could follow? Thanks for all the help


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No problem. Its not really as difficult as it looks. Just go to your local automotive store or electrical store and purchase a 5 pin relay that switches exactly like the one in the diagram. Print the picture and take it with you and the place where you find one should be able to understand what they're looking at so you get the right one.
Then all you do is mount the relay and run the appropriate wires to and from the relay as per the diagram. The ONLY wires you are disturbing which are already on the truck is the yellow wire which is the power wire to the lift pump and the brown wire that goes to the starter. As per the diagram, you are placing the relay directly in the path of the hot lead to the lift pump so the relay switch (pin 87a and 87) is what allows the LP to get power through pin 30 or not. And the brown starter wire is the wire that runs to the starter relay so that when you turn the key to the START position, the brown wire on pin 85 gets power and will activate the relay and then switch the FP wire from pin 87a over to 87 which will cut the power to the LP. Make sense? The only other pin you need to bother with is 86 which is a simply ground wire.:thumbsup:
 

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Discussion Starter · #19 ·
Sounds easy enough! One more question before I tackle this, is this relay found at auto parts store or like radio shack or something?



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Sounds easy enough! One more question before I tackle this, is this relay found at auto parts store or like radio shack or something?



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I think they're pretty common. I found one at my local NAPA and I didn't care for the way it didn't have a mount. I found another one at my local electrical parts store that had a mount so I could screw it to the firewall. I never looked at Radio Shack only because I already found one but they may have one too.:thumbsup:
 
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