Did not expect an electric fuel pump to be such an improvement!

['94IDITurbo7.3]

So with these elec. pumps being more effeciant and having a more consistant fuel pressure would that result in improved mpg?

 

[GenLightening]

That would be really good information to know. My thinking would be, but correct me if I'm wrong, that if you had a higher pressure feeding the pump, it would increase the amount injected by the pump. I might be wrong but it is just my thinking. It would just be good to know the limits of how much pressure would be too much to push into these injection pumps.

Mel did a study on this and more than about 9 psi and the pump timing started changing. I can't remember how much, but too much pressure can harm the pump.

 

[mankypro]

I had trouble maintaining reliable psi with 5's and 13's i changed over to FASS 14psi pumps and never looked back.

Mankypro, I'm in the process of researching a reliable electronic lift pump to replace my failing stock lift pump on my '89 Ford E-250 Club Wagon 7.3 IDI. Spent a few hours reading posts on various forums and have narrowed it down to the Airtex/Master pumps or a Walbro pump. Users have reported mixed reviews on both, but I can't seem to find anything guaranteed to be reliable unless I want to spend $400+, which I am unable to do.

It's been about two years since this post where you praised the Walbro pumps you're using - can you give me an update on how they are working out?

 

[plywood]

I've wanted for years to see good scientific info on whether the difference between 4-14 psi to the IP makes any difference in timing.

I run a facet/carrier duralift wide open and it seems to work just great.

I just don't think that it's a 4+100 makes 104 and 14+100 makes 114 because of the way the transfer pump works.

One good scientific test Mel could have his IP guy do is see as the lift pump pressure is increased, how much of that pressure transfers through the IP transfer pump to increase the housing pressure, and how much this actually causes the timing to advance.

I wonder what the range is in pressure from the pulsing of a factory lift pump if it could be measured that quickly.

 

[hesutton]

One good scientific test Mel could have his IP guy do is see as the lift pump pressure is increased, how much of that pressure transfers through the IP transfer pump to increase the housing pressure, and how much this actually causes the timing to advance.

He did that back in 2009. Here's the results:

There was some debate a while back about the effects of fuel inlet presure on timing. I had negative experiences with a gas EFI pump, and others were running pumps greater than 7 PSI, but less than the estimated 50 PSI that the gasser pump was pushing. Somewhere in between... I said, must be a point at which the presure becomes a factor.

Soooo... I asked my pump wizard about this and he said he didn't know, because normally our pumps are calibrated at about 4 or 5 pounds inlet presure, and he never fooled with varying it. So I said next time I got a pump in your shop, try it and let me know. So, Todd C is getting a Baby Moose. It rebuilt up real nice, and before taking it off the test stand, Mr. Moose Pump ran a battery of tests. What he found was suprising to him, but not to me.

The pump was calibrated and tested between 4 and 5 PSI. The default timing curve was obtained, and the pump certified as being correct. Inlet presure was then slowly increased 1 PSI at a time, and the pump run through the full RPM range. By 9 PSI, the pump had gained a full 1 degree of advance at idle. By 18 PSI, the pump was fully saturated with what was esentially a static unchanging timing of about 12 degrees. There was a somewhat linear curve along the way, with idle producing a greater amount of advance than at 3300 RPM. So the net effect is that an increasing pump presure results in a shorter and shorter timing curve, until it is a flat line. This translates into a Holley Blue or Facet Duralift, taking 1 to 1 and a half degrees of timing variance away from your IP. Not a significant amount to be sure, but at least now you have the facts. Because of this discovery, I will now be asking pump customers what IP inlet presure they would like their pump calibrated to. We may be able to compensate slightly for the difference, but will not really be able to do anything about the decreased range internally available in the pump. At idle, inlet presure seems to have the most effect, as any change in presure upwards from 5 PSI caused some small shift even if it was only a quarter of a degree at a time.

Heath

 

[brettader]

I ended up going with a Raptor 150 fuel pump, and have ordered a block off plate for my stock fuel pump. Can anyone give me an idea what the ideal fuel pressure should be for my engine at both idle and wide open throttle? This pump has a regulator up to 85 psi, so I'm wondering what I should aim for?

 

[snicklas]

The IDI normally is supplied at 4-8 PSI from the Mechanical Fuel Pump, you need to try and stay in that range. If you pit more pressure into the IP, it effects the timing of the pump.

 

[Matrix37495]

Since this thread has gone the direction of lift pump pressure....

What effect will under pressure have on the IP timing? I checked my fuel pressure and i'm only getting 2 psi at the filter head (ordered a Dura-Lift, Thanks GenLightening) and i'm wondering if thats what causes my surging rpms when i slowly open the throttle....

 

[plywood]

He did that back in 2009. Here's the results:




Heath

Thanks Heath, I never did see that one.

That explains another curiousity of mine, which was how much the advance piston can actually advance the timing.

So nothing on the housing pressure??? That would say a lot.

 

[snicklas]

Since this thread has gone the direction of lift pump pressure....

What effect will under pressure have on the IP timing? I checked my fuel pressure and i'm only getting 2 psi at the filter head (ordered a Dura-Lift, Thanks GenLightening) and i'm wondering if thats what causes my surging rpms when i slowly open the throttle....

Fuel starving at higher throttle levels, maybe even trip the Fuel Filter Light.... the IP has the ability to pull a small amount of fuel, and some have even been driving with a bad lift pump. It can happen, but you will starve the IP for fuel.... and remember on the IDI, the fuel lubes and cools the pump, so you could cause damage to the IP from heat.... I think that happened to someone, maybe dyoung, he lost a lift pump, or had a clogged inlet screen on the IP and it caused the pump to overheat and fail..... (It was not his GM Gov Spring Pump, it was another one). Whoever it happened to, I think said the pump, when it failed was to hot to touch..... it may have even seized and broke the shaft in the pump.....

 

[plywood]

I don't know where Heath got that post from so maybe this has been ironed out already.

When I got mine rebuilt about four years ago, I had the conversation with my rebuilder, we talked about what inlet pressure I'd be running, and he said he could calibrate my IP accordingly and it's always ran good.

I wondering if Mel's experiment went further, meaning if the IP was calibrated to run at whichever psi, would it then have it's full range of advance.

I understand the idea that if you have to change the actual IP position to correct for the lift pump pressure that you then flatten your advance curve some, but I'm thinking if you correct it by adjusting the allen at the bottom of the "light load advance" mechanism, you then return the advance piston to where it was by putting pressure in the opposite direction that the higher housing pressure is causing, and then you still have your full range of advance, and still have the full range of retardation caused by increased throttle.