Flathead efi issue

[ken-r-mer]

I'm running a 49-53 Flathead w/ 2 - 1988 Ford Escort EFI throttle bodies controlled by Megasquirt II software. The Ford fuel specs for the Escort throttle bodies is between 35-45 psi. The existing fuel pump is an external unit w/ a fuel filter but no pressure regulator (hmmm). I can't read the info on the pump's external housing.
Recently I noticed a stumble in the engine performance when letting off the accelerator in top gear once achieving cruising speed.
When I got home I noticed the fuel pressure gauge reading around 28 psi. I let the motor cool off and the next day started up the motor and the reading was 38 psi. I took it out for a ride and the stumble reappeared after about 10 minutes of driving. Returning home I had a reading of 28 psi on the gauge, again.
I figure it's either a tired fuel pump or partially clogged fuel filter. So I decided to replace both.
I found a Powerflow EFI fuel pump rated at 45 psi (maximum range of the Escort EFI) with a fuel flow for up to 750 hp (should be adequate for my 180 hp flattie).
My question is....the previous owner had positioned the fuel filter AFTER the fuel pump. Would it be smarter to install the fuel filter BEFORE the electric fuel pump? Could micro sized particles in the fuel, normally caught by the filter, affect the fuel pumps performance, thus causing the fuel pump's early demise? The original pump has only 14,500 miles on it.

[JSeery]

The filter should be before the pump to protect the pump. A filter is always a restrictor to flow to some extent, the finer the filter element the more it restricts flow. One solution is more filter surface area (larger filter). Not sure what type/size filter you are using, but on these applications I use the large canister or spin-on type. I would also add a regulator and a by-pass recirculation system if it doesn't currently have one. I know the Ford 5.0 injectors are sensitive to fuel pressure.

If it was my setup I would use a remote fuel pressure gauge mounting inside the car so I could monitor it during operation (electronic remote gauge). Mount a pressure regulator as near the throttle body as practical with a by-pass back to the tank. And install a spin-on fuel filter. The condition of the fuel tank and fuel can also be issues.

[Kahuna]

I like J's suggestions, but I would also install an in-tank fuel pump.

[JSeery]

I like the in-tank pumps as well, but have also used external pumps mounted near the tank and as low as possible with fairly good success.

[ken-r-mer]

In the case of the '88 Escort EFI bodies, the return lines are in the throttle body. So I do have the return lines, its just that they return from the throttle body and not a fitting just after the fuel pump.

The fuel filter used was a Fram G3727 (used in Asuna, GM, Isuzu, Jaguar, Land Rover, Passenger Car, Pickup, SUV, and Vans).

The fuel tank was a new unit 14,000 miles ago.

[JSeery]

Sponsored Links (Register now to hide all advertisements)

That's a fairly small inline filter, not what I would use. I'm sure it would work if changed on a regular bases, but not what I would use.

BUT then I'm used to large displacement, high performance, high RPM fuel injection systems, this may be over kill for a flathead filter!!! But I'm into a lot of over kill!!! LOL

[Bored&Stroked]

The question of fuel filter placement depends on the application, type of fuel filter and the type of pump. Most fuel fuel pumps are designed to be as close to the tank as possible -- as they "push" far better than they "pull" fuel.

With that said, in many high performance EFI fuel systems, we'll have a larger micron fuel filter before the pump (to protect it from damage due to debris in the fuel) and a much smaller micron fuel filter AFTER the pump - to protect the very small orifices of the fuel injectors from clogging (due to smaller debris).

Almost all the fuel filters I've used in the above situations use a fine mesh screen in them (different micron mesh for before/after) - as they need to flow a lot (high horsepower) and can be cleaned and reused. Also, as most EFI systems have return lines, the overall fuel system flows a LOT more fuel through it, than the actual engine is using at any given time.

Another consideration can be fuel temperature - which can increase rapidly due to the amount of cycling through the system (especially low speed). When a car is idling or in traffic a ton of fuel is being pushed through the system and recycled right back to the tank - and the temperature keeps going up. To help with this, we will use fuel coolers and/or fuel pumps with control modules to slow down the fuel volume in these conditions.

As I'm not familiar with your actual system components, the above may be off base - just wanted to throw it out there just in case some of it applies.

Best of luck!
D

[41Joe]

Other than the fuel pump issue, how do you like your EFI setup? Any pictures of your flattie?

[5851a]

That sounds like a trick setup. Don't have anything here to look at but I thought the CFI throttle bodes had a pressure regulator built into them. The factory efi that I've worked on just used that strainer sock before the pump and filter after like Bored and Stroked said.

[JSeery]

Could be, I'm more familiar with fuel rails and individual sequentially fired injectors. Factory fuel rails have builtin pressure regulators and bypass.

[Ol' Ron]

Doee your system also control the ignition. I'm building a system for my Flathead using a 4.2 throttle body and distributor. However i have to have a new chip burned. Will try thie ignition part first with the carb to see if I can control the timing as I need.