Jump to content
Ultimate Subaru Message Board

Recommended Posts

So the SPFI conversion on the Brat's EA81 runs quite well so far....

 

The idle quality was not what you would call.... lets see here..... good? :rolleyes:

It was wandering a bit, and idleing rough. Now the Weber ran baby-bottom smooth, so I knew it was FI related. I started checking parts, and replacing stuff with JY bits to verify. Soaked a low mileage IAC in some knarly carb cleaner overnight - looks like new. Nothing changed. Changed the MAF, CTS, TPS (and adjusted) - no change. Adjusted the timing (third or fourth time), adjusted the idle screw, cleaned stuff.... followed by hand wringing and teeth gnashing..... beer...... scour EA82 FSM for several hours....

 

And then I decided to look into the fuel pressure. I don't have a guage - which presents a new set of problems. I put the fuel pump to my ear and my hand on the intake duct (don't ask how this is possible - it just is with my temporary ghetto fuel pump mounting situation), and I could hear the fuel pump "chewing" (for lack of a better term) in time with the roughness of the engine. I said to myself: "Self - clearly you have a fuel pump problem" followed closely by: "Doh.... Self - you should have bought a spare". I did get a spare today only to find that it's also dead (well technically I guess you might say it's sleeping - if you give it power and then smack it real hard it will take off for a bit.... hibernation perhaps?). I then decided that maybe it just needs a cleaner power supply - wired up a second relay for it, and used the ECU power for the relay control instead. That helped about 50% I would say. I can still hear the pump "chewing" although it's not as loud now. Engine smoothed out, and seems quite a bit better. I'm looking for more tho.

 

So I want some opinions on what this chewing might be? Pump bearings? It seems to have been reduced by applying a 14 guage power supply direcly through a relay, but it's still there. The pump is a long way from the tank. FI filter is newish, as is the carb filter down by the tank..... now on the SPFI cars they don't have a filter under the car - is that because the pump is so beefy that it can chew through anything that gets past it's little screen filter?

 

I'm sick of spending money I don't have on junk yard pumps. I may take this little $16 gem back and see if they will let me swap it out, but who knows if that will happen. Should I go the Ford pump route instead?

 

Should I have a filter before the pump and after it? Or shall I eliminate that one by the tank? Maybe it's too restrictive? The SPFI pump puts out a LOT of fuel, and it seems that whatever is not needed to maintain the SPFI pressure the regulator just sends back to the tank - that makes for a TON more fuel going through the lines than the carb had. Maybe the smaller return line is stressing the pump?

 

Am I making all this too complex? :-\ I do that a lot....

 

GD

Share this post


Link to post
Share on other sites

You should probably mount the fuel pump as close to the tank as you can. They're not designed to pull fuel very far, its more designed to push the fuel.

 

Also, I'd drop the fuel filter before the pump. Try to mimic the EA82 Fuel system as close as possible.

Share this post


Link to post
Share on other sites

Want to try some more "ghetto"? Try putting some sort of fuel plenum (for lack of a better term) before the pump that you can route the regulator's return flow to (or at least most of the flow from it). This might help you two ways: Reduce the strain from the suction head for the pump to raise the full volume from the tank to pump level, and reduce any possible strain trying to push the return fuel back your vent line (or whatever you are using for fuel return).

 

I had considered something like your temp setup for doing an SPFI conversion, so it would be nice to see if this works.

Share this post


Link to post
Share on other sites

Interesting - so you are sugesting I route the pressure regulator return back into the pump supply line before the pump inlet? That's an interesting idea...... I guess it's similar to returning it to the tank, but instead it's getting retured to a point right before the pump. That sounds potentially dangerous and crazy, but ya know I have a feeling it might work. I like it :lol:

 

I think I'll get some fittings and give that run.

 

GD

Share this post


Link to post
Share on other sites

I'd say do as mike says... I did this conversion on a BRAT and I put it in the stock brat location... hey speaking of that... you DID get rid of the old fuel pump and filter right?:-\ Also make sure you have a good ground for the pump....

Share this post


Link to post
Share on other sites

I had a similar case and i understand the noise is cavitation, the pump is struggling to 'pull' the fuel. The pump needs to be very close to the tank and low, with minimal restriction. A reason pumps are often mounted intank, and external ones have large intake piping.

 

If the fuel pressure is too high the pump will 'groan' and the engine will tend to overfuel, you could eliminate the return line as an issue by feeding the return from the fuel pressure regulator into a container and seeing if that reduces the load. At the same time you can check the fuel flow, at idle (full vacuum) you should get at least 1.8 litres/ minute fuel flow. A 5/16 size line is fine for fuel lines up to 3 litres / minute, and more. I think 1 US gallon = 3.78 litres.

 

You need some kind of strainer before the pump, on my offroader i have a normal carbed engine style fuel filter between tank and an EA82T pump, with the pump mounted level with the bottom of the tank, total intake piping = about 12 inches and its fine.

Share this post


Link to post
Share on other sites
I had a similar case and i understand the noise is cavitation, the pump is struggling to 'pull' the fuel. The pump needs to be very close to the tank and low, with minimal restriction. A reason pumps are often mounted intank, and external ones have large intake piping.

 

That makes sense - cavitation would indeed explain the noise. Hadn't thought of that, but I've seen similar things with water pumps and such on other brands. I'll go ahead and move the pump under the car then.

 

Older RU's had the carb pump mounted in the engine bay, so I figured maybe it wasn't such a big deal. The increased fuel demand of the SPFI seems to cause a hail of issues - all part of the fun.

 

I'd say do as mike says... I did this conversion on a BRAT and I put it in the stock brat location... hey speaking of that... you DID get rid of the old fuel pump and filter right?:-\ Also make sure you have a good ground for the pump....

 

Yeah - initially I had thought that the carb pump could maybe help supply the fuel injection pump. That turned out to be not possible however since when the carb pump is not running the FI pump cannot draw through it. A complex chicken and egg problem results with the SPFI pump unable to draw enough fuel to pressurize the system, and the carb pump unable to run fast enough due to the engine not catching, and not supplying a decent voltage. In practice this resulted in the engine not even attmpting the start. On paper you might expect to see it sputter a bit at least, but it would take more cranking than I was willing to do to get the FI filter full, and the system up to 24 psi. I bypassed it with a length of hose. The carb filter is still in place, and maybe I should just remove that and give it a try. Can't hurt to give it a go. I have always planned to move the pump down there anyway, but it's been about 105 here every day in the shade, and I'm not looking forward to a hot driveway, and gasoline running into my oh-so-sweaty armpit. YUM!

 

At least after I get it all worked out, the rest of the system should be good to hook. I've cleaned, tested and replaced near every part of this SPFI setup - it came from 258k miles of rough stoner snowboard duty - it's parent wagon couldn't take it anymore and did itself in with a tree. :eek: The SPFI system was defiant to the very end - manging to kill off the body (totaled), engine (punctured oil filter, and drove till it seized), and transmission (stuck in 2nd gear by the obviously considerable force of the impact). I think I got the only usable part left on it..... y-pipe looks alright too, and the wheels live on (motion alloys) on the kid's next victim.

 

GD

Share this post


Link to post
Share on other sites

the car I bought for my own FI conversion did not have the fuel pressure regulator on it and had to be removed several years ago...I only knew this later when reading the various repairs that had to be done on this car...although the car runs very smooth, under what conditions of driving style is the fuel regulator needed and how does the car behave when it is being over fueled...I am asking the question to determine if I should purchase another regulator...

I had a similar case and i understand the noise is cavitation, the pump is struggling to 'pull' the fuel. The pump needs to be very close to the tank and low, with minimal restriction. A reason pumps are often mounted intank, and external ones have large intake piping.

 

If the fuel pressure is too high the pump will 'groan' and the engine will tend to overfuel, you could eliminate the return line as an issue by feeding the return from the fuel pressure regulator into a container and seeing if that reduces the load. At the same time you can check the fuel flow, at idle (full vacuum) you should get at least 1.8 litres/ minute fuel flow. A 5/16 size line is fine for fuel lines up to 3 litres / minute, and more. I think 1 US gallon = 3.78 litres.

 

You need some kind of strainer before the pump, on my offroader i have a normal carbed engine style fuel filter between tank and an EA82T pump, with the pump mounted level with the bottom of the tank, total intake piping = about 12 inches and its fine.

Share this post


Link to post
Share on other sites
just curious GD..did you have the O2 sensor hooked up yet or did you wait to see if the rest works fine first before hooking up the O2

 

I first started it with no 02, but only to verify my wireing and such. It did run without it as I knew it should, but ran pretty poorly. I installed the 02 the next day. Had to swap y-pipes with my wagon, as it had the feedback carb originally, and now has a Weber so was equipped with the 02 Bung (what a great word eh? Just not a lot of situations where you can use the word Bung)

 

As for the Pressure Regulator.... that's an inegral part of the throttle body assembly, and cannot be removed... perhaps you mean they removed the one of those pressure pulse reducer things - in which case yes it will run fine without those.

 

GD

Share this post


Link to post
Share on other sites

yes, you are correct, I went to re-read the work order and it was something to do with the pulse thingy, which was by-passed....

I first started it with no 02, but only to verify my wireing and such. It did run without it as I knew it should, but ran pretty poorly. I installed the 02 the next day. Had to swap y-pipes with my wagon, as it had the feedback carb originally, and now has a Weber so was equipped with the 02 Bung (what a great word eh? Just not a lot of situations where you can use the word Bung)

 

As for the Pressure Regulator.... that's an inegral part of the throttle body assembly, and cannot be removed... perhaps you mean they removed the one of those pressure pulse reducer things - in which case yes it will run fine without those.

 

GD

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×