Megasquirt2 Install AMC360 TBI 83' Cherokee

[myk]

Originally Posted by chrism

What type of signal does that fuel pressure sensor put out?

It's a linear 0.5-4.5v output, below is a link to the sensor specs

http://www.aemelectronics.com/100-ps...99k2mk6ancm0r3

[tgreese]

Mike, thanks for the detailed reply.

Originally Posted by myk

...
I will mount it in the frame rail as low as possible and as close to the tank as possible. That's about the only option I can see that I have.

I wondered about this issue. I've done a little armchair TBI-ing and it seems the alternatives are either an in-tank high-pressure pump, or a second low-pressure pump that fills a surge tank, before the external high-pressure pump. Then your high-pressure pump can be placed at any location below the surge tank, even in the engine compartment.

Making a surge tank with a spin-on fuel filter looks straightforward, ala http://www.midnightdsigns.com/james/FuelSystem.htm

[tgreese]

Originally Posted by myk

...

I'm planning on using a 36-1 toothed wheel on the crank pulley for the tach signal plus a one tooth sensor in the distributor both using Allegro gear tooth sensors (had great experience with this setup on past installs)

...

Mike, I'd like a little more about the one tooth sensor in the distributor, if you've gotten that far. Why do you need a cam sensor? You already have the crank sensor, which you could divide by 2 (big gap) or 72 (small gaps) to get the one tooth input from the distributor.

I presume you can make this from a Motorcraft distributor by grinding away seven of the reluctor tabs. You could even use the existing VR trigger, though you said you wanted to fit a Hall effect trigger.

I found some discussion of capability in the MSExtra docs, but no explanation of reasoning. I expect you have thought about the issues, and I would be interested in your reasoning.

[myk]

I've seen that type of setup before and was always curious why the low pressure pump wouldn't encounter the same issues that the high pressure pump would? maybe the design is better suited to pull fuel?

If I mount the pump on the frame as low as possible it should be right at the same level as the bottom of the tank, this would seem to be the equivalent of an in-tank pump, the only difference being the longer run of hose to the pick-up which could be a substantial issue?

I'll try it out and see how it behaves, I have the fuel pressure sensor so It will be easy to see any issues. Thanks for the diagram that could be a good back-up plan if I have issues when the tank is low.

Mike

[myk]

Originally Posted by tgreese

Mike, I'd like a little more about the one tooth sensor in the distributor, if you've gotten that far. Why do you need a cam sensor? You already have the crank sensor, which you could divide by 2 (big gap) or 72 (small gaps) to get the one tooth input from the distributor.

I presume you can make this from a Motorcraft distributor by grinding away seven of the reluctor tabs. You could even use the existing VR trigger, though you said you wanted to fit a Hall effect trigger.

I found some discussion of capability in the MSExtra docs, but no explanation of reasoning. I expect you have thought about the issues, and I would be interested in your reasoning.

For the current TBI install your right, I do not need the cam sensor as it is non-sequential fueling and still uses the dizzy to distribute the sparks. I was thinking ahead if I switch to sequential MPFI and/or COP in the future I would already have the hardware and wiring setup for it. The sequential code needs to know engine cycle phase which it cannot get from the crank sensor alone i.e. it cannot tell between TDC compression and TDC exhaust with only the crank sensor.

That's exactly what I planned with the dizzy was cutting all but one of the vanes away and replacing the VR with a hall sensor (they just work better imho). The code only uses the cam signal for phase info and uses the crank trigger for the actual precision timing so the cam sensor accuracy is not very important just needs to know if its on compression or exhaust.

Mike

[tgreese]

Originally Posted by myk

I've seen that type of setup before and was always curious why the low pressure pump wouldn't encounter the same issues that the high pressure pump would? maybe the design is better suited to pull fuel?

I don't know - but I do know that lots of people have used the low pressure electric fuel pumps with carburetors, and I don't recall any worries about mounting the pump low. The usual advice is "as close to the tank as possible."

One approach I've been mulling over: use the original mechanical pump to fill the accumulator. This would retain all of the factory fuel plumbing aft of the engine compartment. Certainly the mechanical pump is capable of drawing fuel from the tank, rather than pushing it to the front of the car. The accumulator approach would also radically shorten the length of the high pressure circuit, which I believe would be a net plus, both in terms of simplicity and peak pressure / fuel delivery rate.

If I mount the pump on the frame as low as possible it should be right at the same level as the bottom of the tank, this would seem to be the equivalent of an in-tank pump, the only difference being the longer run of hose to the pick-up which could be a substantial issue?

I would think so, except for the additional drag with the longer inlet path. This is equivalent to a pressure differential across the input path that the pump must overcome. By mounting the pump higher or lower, you are changing the gravity term in that equation. Mount the pump low enough, and the weight of the fuel column overcomes the drag, and fuel comes out the inlet without pumping. The hydrodynamic (petrodynamic?) drag doesn't change with the mounting height - instead the drag depends on the path length, curvature, and pipe diameter. So if your combination of these factors doesn't starve the pump, it'll work.

Probably overly analytical, but maybe of interest.

[chrism]

On your fuel system. I took the sending unit that looks similar to your pics.
Cut the bottom portion of the tube off and clamp some vice grips to the top portion. Heat the tube from the top with a torch and the existing solder will melt. You should be able to pull the tubes right out. Re-drill to the proper size make your new tubes and solder them back in.

What we found that works well (especially in the coffin shaped tanks) is using two or more of these pickups in the bottom of the tank. They will get your pickup right down to the bottom of the tank and provide some filtering.
http://www.autoperformanceengineerin...l/pickups.html

Your Walbro pump is the equivalent of the Airtex E8248 which is the higher performance version of the E2000. I have heard good things about the Walbro pumps. I use the E8248 mounted on the frame rail with the walbro pickups to feed my LT1 and it works well. The problem I had before I added the pickups was that when I got down to less than 1/2 tank and hit the brakes the fuel would head to the front of the tank and starve the pump (the sock on the stock pickup was also shot which made this even worse). So now I have two pickups. One directly to the bottom of the tank from the sender and one that extends up towards the front of the tank. No more starvation issues.

This summer I plan on replacing the stock tank completly with a rear mounted S10 blazer tank that has an in tank setup with the proper EFI baffles inside the tank. I am hoping that in addition to a better fuel delivery system it will also help with the buildup of junk that tends to rot out the driver side frame rail .

[myk]

Originally Posted by chrism

On your fuel system. I took the sending unit that looks similar to your pics.
Cut the bottom portion of the tube off and clamp some vice grips to the top portion. Heat the tube from the top with a torch and the existing solder will melt. You should be able to pull the tubes right out. Re-drill to the proper size make your new tubes and solder them back in.

What we found that works well (especially in the coffin shaped tanks) is using two or more of these pickups in the bottom of the tank. They will get your pickup right down to the bottom of the tank and provide some filtering.
http://www.autoperformanceengineerin...l/pickups.html

Your Walbro pump is the equivalent of the Airtex E8248 which is the higher performance version of the E2000. I have heard good things about the Walbro pumps. I use the E8248 mounted on the frame rail with the walbro pickups to feed my LT1 and it works well. The problem I had before I added the pickups was that when I got down to less than 1/2 tank and hit the brakes the fuel would head to the front of the tank and starve the pump (the sock on the stock pickup was also shot which made this even worse). So now I have two pickups. One directly to the bottom of the tank from the sender and one that extends up towards the front of the tank. No more starvation issues.

This summer I plan on replacing the stock tank completly with a rear mounted S10 blazer tank that has an in tank setup with the proper EFI baffles inside the tank. I am hoping that in addition to a better fuel delivery system it will also help with the buildup of junk that tends to rot out the driver side frame rail .

Interesting pickup, so to be clear you used two of these in series inside the tank, one of the T-style pickups and the other just a std single port? What kept the fwd one in position right side up? It says they are 3" in dia, will that fit through the opening in the tank? looked smaller than that. Seems like if the aft one started sucking air the fwd one would be useless, read something about how they work but didn't seem totally logical.

Thanks a bunch for the info guys, I only want to do this tank once.

[tgreese]

The pickups are interesting.

If I understand their claim, they say that the pores of the 100% submerged pickup will pass fuel through at some rate. When the pickup becomes exposed to air, the fuel now forms little bubble surfaces across each window in the mesh.

When you have an air-fuel interface, the molecules of fluid are attracted only to other fluid molecules, not the air - thus the surface pulls in on itself, away from the air. This is surface tension.

There is still a negative pressure behind the mesh, caused by the fuel pump. The surface tension is enough to lift the mesh toward the pickup, and shut the inlet valve.

Thus an exposed pickup that is sufficiently wet with fuel will shut itself off from the fuel pump (negative) pressure.

[myk]

I spent a good portion of the night cleaning the tank up inside and out, turned out great but was alot of work.

After looking things over in more detail I'm getting more concerned about my original plan on the fuel delivery, the shape of the tank and the height of things isn't looking good. I'm starting to lean towards that system that Tim posted ealier with the accumulator, read up on it and seems it works pretty darn good for people.

I believe I can fit the accumulator and the HP pump on the driver side inner fender with the accumulator toward the radiator support under the coolant tank and the pump just behind and above it slightly. The LP pump should fit in the area right behind the tank which would be as close as possible to the tank pickup. I'll still install the oversized return and supply lines in the tank. What do you guys think I should do for a pickup in the tank, just run the hard line down to the sump area or get some sort of pickup or sock like posted above? just a single pickup I assume?

The only negative to this I can see is a little more complexity/cost and the reliability factor of two electric pumps.

Mike

[tgreese]

Can't address your pickup issue.

Re the accumulator etc. I have read reports that mounting the fuel pump on the body will be noisy. You may be able to hear the thump-thump-thump of the fuel pump, resonating with the body. Frame mounting should be quieter. I would think that you could mount the pump on the frame rail below the accumulator. Same general location but more isolation of the pump noise.

[myk]

Found all the parts locally to make the accumulator and LP pump setup. Tim, are you talking about the Carter LP pump being noisy or the Walbro HP pump? I had heard also that the Carter pump is quite loud, however it will be mounted down aft of the tank. I don't think the Walbro HP pump is too loud, I'll have to see if there is a spot on the frame rail for it, my intention was to keep it well away from the headers and just a short run of HP hose to the TBI.

As for the pick-up, I'm just going to run the 3/8" hardline down to within ~1/4" or so of the bottom of the sump in the tank and see how it works, it's pretty easy to remove the pickup through the access hole in the floor so if I need to change it later it won't require dropping the tank. The accumulator holds a quart of fuel so it will run quite a while on that if the pickup gets air temporarily.

Glad you guys suggested the above ideas, I think this will be a better solution.

Mike

[tgreese]

Originally Posted by myk

Found all the parts locally to make the accumulator and LP pump setup. Tim, are you talking about the Carter LP pump being noisy or the Walbro HP pump? I had heard also that the Carter pump is quite loud, however it will be mounted down aft of the tank. I don't think the Walbro HP pump is too loud, I'll have to see if there is a spot on the frame rail for it, my intention was to keep it well away from the headers and just a short run of HP hose to the TBI.

As for the pick-up, I'm just going to run the 3/8" hardline down to within ~1/4" or so of the bottom of the sump in the tank and see how it works, it's pretty easy to remove the pickup through the access hole in the floor so if I need to change it later it won't require dropping the tank. The accumulator holds a quart of fuel so it will run quite a while on that if the pickup gets air temporarily.

Glad you guys suggested the above ideas, I think this will be a better solution.

Mike

Mostly thinking about the Walbro. Will Marsh at BinderPlanet http://www.binderplanet.com/forums/s...ad.php?t=53524 used a similar setup to what you propose, and complains about the noise from the HP fuel pump, mounted on the inner fender. He uses a NAPA replacement part for a E100, which should be an Airtex. Maybe the Walbro is quieter ...

[myk]

Was able to get all the fuel system parts today, looking like the only spot in the engine bay for the accumulator is on the driver side of the radiator support below the overflow tank, should work just fine though. I was surprised how big the filter/accumulator is. Was able to get the spin on filter base from Shucks/O'reilly it's a Fram HPK2. Picked up the LP pump a Carter P4070, and the accumulator filter a NAPA 3281 both from the local NAPA store. Just need to add an extension tube and a return port on the filter base.



Also snapped a pic of the Innovate LC1 WBO2 sensor in the exhaust, I put it in the Y after the headers and before the muffler.



Mike

[myk]

Finished adding the 3/8" lines to the tank pick-up, unsoldered the old ones oversized the holes and soldered the new one back in, also soldered two little brass rings on the upper ends so the hoses can't slip off. I ran the pick-up line straight down to the bottom of the sump in the tank with 1/4" clearance to the bottom I left the flared end on there so it wasn't a sharp edge, the return line I faced to the front of the tank and a little higher attempting to aim it away from the pick-up as much as possible. Also added the return port on the accumulator. Getting close to putting the tank back in and getting things plumbed.

[myk]

Here's the accumulator finished up, the main inlet and outlet are 90deg 3/8" barbed hose to 1/2" npt brass fittings (had to shorten these a bit so they would spin around without hitting each other), the tank return that I added is a 1.5" x 1/8" npt brass pipe fitting to a 90deg to 3/8" barbed hose, the extension tube to feed the HP pump is a piece of copper tubing silver soldered to the inside of the threaded filter attachment. The filter is a NAPA 3281 and the housing is a remote oil filter housing made by Fram p/n HPK2.

[myk]

Back on the project now, took a break from it for a while. I have the tank back in temporarily to check the clearances for running the new fuel lines. Planning on running the new 3/8" steel lines in place of the originals between the tank and frame rail, appears to be just enough room. I installed the low pressure carter pump right behind the tank on the upper crossmember. Also mounted the megasquirt on the top side of the drivers side inner fender. Mounted the accumulated to the radiator support and the HP pump and filter to the inner fender as well...hopefully it won't be too loud there, we'll see.

[myk]

Major progress the last two days...I've got all the fuel lines installed and the fuel tank back in, glad that part is over, big job. The fuel lines are 3/8 steel which is tough to work with but should last a while. Here's a bunch of pics of the installation, the tee fitting in one of the pics is where the two return lines (one from the TBI and the other from the accumulator) come together and head back to the tank. Next up is the wiring which is easy in comparison, should be ready to fire it up in the next week or two...















Mike

[myk]

Completely finished plumbing the fuel system and tested the pumps out this weekend, everything works as it should, set the FPR at 15psi to start with. I also checked the pressure on the return line with both pumps running wide open and there was no pressure building so that is a good sign that the return system is more than adequate. I was worried about the noise of the Walbro HP pump on the inner fenderwell but the funny thing is that the Carter LP pump in the back is the louder one of the two, the Walbro just hums along nicely in the engine bay noise isn't bad at all, I don't think I'll be able to hear either one with the engine running though. Yesterday I started in on the wiring harness, shouldn't be much longer now...will post some pics when I get a chance.

Mike

[Bill USN-1]

You did a nice job and it looks good but I feel you made things more complicated and worse off then they should have been.

The lift pump isn't needed and actually adds another fail point in the system.
The main pump works fine if mount at or near the bottom level of the tank and close to the tank.
Pumps push much better then they pull and work less.

You have also mounted the pump in the engine bay which induces heat directly to the pump(headers!) and yes, EFI can and will vapor lock if too much heat is introduced.
With a constant return system, all the heat in the fuel as it passes through the engine bay will be returned to the tank. Over time the heat will continue to build.
Heat is also the #1 killer of the pump. And now you mounted right next to the hottest temp created by the engine. How many factory installs have the EFI pump mounted in the engine bay? Most are in the tank to use the fuel to cool them.

I'm not telling you what to do but I have tried most different installation methods and had to fix many. Just trying to save you some frustration.
Even seen guys use the stock engine pump to feed the efi pump.

The method I documented on BinderPlanet works.

If you do nothing else then at least add heat shields around the pump.