So who has bumped the power on a 6CTA cummins

charlesmann

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Basically it's the whole banjo bolt that connects the fuel return line to the injection pump. It has a small wire spring in it and a ball bearing and seat that act as a pressure relief valve. They're very susceptible to corrosion and wear. This bleeds off internal fuel feed pressure in the pump which causes power loss, and in extreme cases even causes hard starting.

It's the banjo bolt in the line coming off the side of the pump at the front end. Don't buy a factory replacement. They're junk. Google " Torktec OFV-20" and buy that. They have stainless internals, stainless spring, and a hardened seat. They're also adjustable so you can raise your fuel pressure, but they come preset at factory spec.

Higher feed pressure will provide more power all by itself.
So, could a person do as with the 5.9s and route the return back to the line in side of the of the pump. Then fuel pressure is maintained on the line in and return side of the pump.
 

Jeepsinker

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So, could a person do as with the 5.9s and route the return back to the line in side of the of the pump. Then fuel pressure is maintained on the line in and return side of the pump.
You could, but the only benefit there is if you have an engine that consumes enough fuel that you need larger feed hose and dual inlet ports to the injection pump, along with a much higher performance fuel supply ( lift) pump.
There is no conceivable instance where anyone would benefit from that on these trucks unless you're up over the 1000 horsepower mark and using it to sled pull. In other words, you'd need much more radical power modifications to render that a necessary upgrade. This isn't like the NHC250 where a dual feed will benefit a stock configuration.

You'll see more benefit simply raising the pressure with the adjustable valve while still allowing hot unused fuel to bypass and help cool the pump.
 

WillWagner

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The stock lift pump, well the newer versions of the pump that came on the engines in the 900 series trucks, is capable of upwards of 70 psi. If you still have the original, small bodied lift pump, you can upgrade it to the newer style and adjust the relief pressure to around 40 psi and the engine will run better.

What the overflow valve does is create the correct low pressure so that the fuel pump can create the correct high or injection pressure. The bosch pumps aren't like the PT or multi fuel pumps as in having the ability to suck fuel. They need boosted pressure to keep the gallery pressurized and free of air voids so the correct high pressure and injection timing. Yes timing, not the base engine or pump timing, but the timing of the fuel into the injetor/cylinder. Remember, airiated fuel compresses and solid fuel won't. When airiated fuel happens, the timing is late causing white smoke, hard or no start and funky power.
 

Patriot6X6

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I did not prime the system because I didn’t know it needed to be done. Only a little bit of fuel dribbled out so I didn’t think it needed to be done. I thought my problem was the different hole placement between the 2 parts. Then when I put the old one back in and it still didn’t start it really surprised me. It ran good before I changed that out.
 

Lukes_deuce

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Also, on a separate note, I have adjusted 3 of the 4 you mentioned, pre-boost fuel, fuel rack and gov springs. If you open the fuel all the way, you will melt the motor. I have 3 threads showing on the rack and a couple turns out on the pre boost. Huge improvement and still usable power but will get warm so you will need to watch EGTs. I have not messed with the star wheel yet. Its an adjustment on how the fuel rack is applied, basically under boost conditions. Also to note, too much pre boost fuel and you will get excessively hot as well. There is a balance to get more usable power. The gov springs give you more RPM so went it shifts, you dont fall back into too low of RPMs. I like to shift at 2300. Another cheap improvement would be to increase the timing.
 

WillWagner

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Put the new valve into the banjo, if only threads are showing.....remember to put the sealing washeres on both sides....it will be fine. Use the lift pump primer button until you hear a hiss at the pump. Foot tothe floor when cranking, it will start.
 

Patriot6X6

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Thanks for the info. I will try it when I get home from work tonight. I really want to adjust the gov springs but I am still a bit nervous. I know a little about turning wrenches which is enough to get me in trouble. Lol. This is why I am asking very basic rookie questions and getting overly concerned when something doesn’t work right.
 

WillWagner

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Your best bet is to leave it alone. The overflow valve is a very common item that fails. I'm sure that after you install it, you will notice a bit of a difference.
 
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Patriot6X6

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I get where you are coming from willwagner but when I first picked up my truck it ran but was very weak on power. Since then I replaced all the fuel filters and fuel lines and cleaned everything up. I did see a difference in performance and power but still struggled starting off the line and pulling even little hills. So I decided to tweak the pre boost fuel screw 3 turns out and 4 clicks on the aneroid valve and such a difference off the line and on straight away. It’s like night and day but I still lag big time on hills so this is where I am at now. Looking for minor harmless little tweets to give me a little more pull up hills.
 

Mos68x

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I get where you are coming from willwagner but when I first picked up my truck it ran but was very weak on power. Since then I replaced all the fuel filters and fuel lines and cleaned everything up. I did see a difference in performance and power but still struggled starting off the line and pulling even little hills. So I decided to tweak the pre boost fuel screw 3 turns out and 4 clicks on the aneroid valve and such a difference off the line and on straight away. It’s like night and day but I still lag big time on hills so this is where I am at now. Looking for minor harmless little tweets to give me a little more pull up hills.
Outside of the things you’ve already addressed, such as filters, the thing that made the biggest difference was when I had my injectors overhauled. I had tried the cleaners but they weren’t able to get them clean for some reason. Maybe because of the JP8 we had to use in the Army?? Either way it might be the same for you if you chase all your adjustment options and still aren’t satisfied.
 

Patriot6X6

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Just got done putting the new OFV back in. Took a little bit of work priming it but it finally turned over. Took it for a ride and definitely better throttle response and more power on the straights but not much difference on the hills.
 

Jeepsinker

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Just got done putting the new OFV back in. Took a little bit of work priming it but it finally turned over. Took it for a ride and definitely better throttle response and more power on the straights but not much difference on the hills.
Alright, now you can start turning your fuel up. Never a good idea to do tuning with bad components in the system.
I can't remember at the moment if the MW pump has a fuel plate like the P7100 does ( it's very late and I'm very tired), but that's where I'd start.
 

Patriot6X6

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Already thinking about it but first I need to turn the fuel screw back in a turn or 2. Now that I am getting more fuel pressure I am getting a lot of black smoke when I take off in first. Clears up pretty quick but I think it may be too much. My pump does not have the fuel plate. It has the full fuel screw in the back with a tamper proof screw in the cover.
 

Patriot6X6

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No. I am actually looking through the site now for ideas. I was hoping to find some gauge ideas as I want it to look like it belongs and not like I pulled it out of a race car.
 
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