Feul Pressure Change....

[icanfixall]

Well I finally got to see if my electric pump change did anything to my timing advance... I went from 3 to 4 lbs pressure up to now a firm 7 lbs.... No timing change was found... I recall reading what Mel had posted about increasing fuel pressure. He found that any increase in pressure advances the timing about 1/4 degree per pound. I really expected to see a timing change... Nope... I'm thinking my timing didn't change because I stayed down below the 9 lbs point. I understand increasing the pressure above 9 or so will advance the internal timing. My shop manual states the normal pressure from the mechanical lift pump is ..... I think its 7 lbs.. Strange that its not listed in there...

 

[Diesel JD]

Not real surprising. I asked RLDSL about this potential problem when adding the Carrier fuel pump and he said he checked the timing with the thing regulated down to 7 psi and without the regulator and there was no difference. I'm thinking you have to go far above the recommended range to see the changes in timing that we've discussed at least above 9-10 psi. I think the spec for the factory lift pump is 4-7 psi but that's what I've seen here and perhaps in the Haynes manual for a cranking test. It would be interesting to see where the pressure starts to be a real issue, but as long as it has enough to keep the IP from starving and not have a dramatic effect on timing I'm not too concerned.

 

[Agnem]

You won't see a timing change until the external pump presure surpasses what the internal pump presure is.

 

[icanfixall]

What I have found is my rig sounds and drives much better now. Robert (RLDSL) and I talks some about the holley red pushing too much volume of fuel thru the system. We both felt the way these return line setups are put together they just can't handle all the fuel the red pushes thru them. I just know my motor sounds and runs differant now. The power flows smoother and I have more of it... The butt dyno is telling me this...

 

[hesutton]

Gary, I'd be surprised if the Holley is putting anywhere near 97 GPH while fueling these IDI's. That rating is at free flow only. There is no way it is putting that kind of volume through the lines, filter, and into the IP runing at cruising RPM.

I don't know what the stock mechanical fuel pump is supposed provide an hour. But, when testing the pump, you are supposed to get at least 1/3 of a pint in 10 seconds at cranking RPM. So that is roughly 1 gallon every 2 minutes, which will be around 30 gallons hour (again at cranking RPM). You know that pump will put out much more than that at driving RPM. So volume may not be as big a factor as pressure. As, it appears the stock lift pump is putting out way more fuel than can be used as well.

My Holley Red is having significat trouble providing fuel pressure with the Moose IP/Injectors on the truck. Fuel pressure is now typically 0.5 psi at full throttle, and only 1 psi at moderate acceleration. Mel has reported a similar finding as well. Too bad we don't know the volume to go along with those pressure readings.

Heath

 

[Agnem]

I'd have to hypothesize that the Moose Pump is drawing darned near the full output of 97 GPH from a Holley Red. The loss of fuel presure pretty much indicates it is sucking the fuel from the line as fast as the Holley can put it in. The volume is there, but the presure isn't.

 

[icanfixall]

Gees Mel... That really sucks.... I recall a posting some time back about fuel pressure running a hloey red and a Moose pump and wide open throttle. I don't recall too much about that posting but it was interesting... I thought maybe the rig was Heath's rig.... When I dyno my truck I will be watching the fuel pressure and report back the findings... The carrier pump sure is quieter running than the holley red. I even had a 1/4 inch piece of rubber between the mount and the frame.... Still buzzed like hell.... Towcat can attest to that noise... But on the plus side I know when the pump was running....

 

[hesutton]

I can't hear my Holley Red at all. Once the truck is running that's all I can hear.

Heath

 

[icanfixall]

Heath... I could hear mine running even over the motor running... I was just reading my posting line "Feul Pressure Change".... Had no idea I spelled fuel wrong.....Must be getten old.....