Mechanical Fuel Pump Options

[dennisonwj]

I have bought a multi-owner 1988 Jeep Wrangler YJ with a 4.2L. A previous owner placed a Mr. Gasket electric fuel pump in the ENGINE BAY (huge NO NO via the manufacture, all over the instructions not to, PO did it anyway, DUMB).

I would like to get all the messy PO aftermarket garbage out of this jeep and get it back to stock SO I can modify it with a bunch of my own stuff. I want it to be at a baseline. Plus, I tend to be a rather particular about wires connections, cleanliness, etc. PO WAS NOT.

What mechanical fuel pump does the forum recommend to turn this back stock?

It has had the horrific Carter carb. replaced with a Weber and that upgrade is staying (the electric fuel pump seems to be drowning the carb. it runs super rich). I am hoping the mechanical pump will help me tune it better.

 

[PoliceMonkey161]

I have bought a multi-owner 1988 Jeep Wrangler YJ with a 4.2L. A previous owner placed a Mr. Gasket electric fuel pump in the ENGINE BAY (huge NO NO via the manufacture, all over the instructions not to, PO did it anyway, DUMB).

I would like to get all the messy PO aftermarket garbage out of this jeep and get it back to stock SO I can modify it with a bunch of my own stuff. I want it to be at a baseline. Plus, I tend to be a rather particular about wires connections, cleanliness, etc. PO WAS NOT.

What mechanical fuel pump does the forum recommend to turn this back stock?

It has had the horrific Carter carb. replaced with a Weber and that upgrade is staying (the electric fuel pump seems to be drowning the carb. it runs super rich). I am hoping the mechanical pump will help me tune it better.

The Mr Gasket fuel pump is not a bad pump in itself, it is installed incorrectly as you pointed out and beyond the improper location, its not likely setup for your Weber. I would not recommend a mechanical pump with your Weber. With a few exceptions, the Weber prefers a constant (mech pumps cause the fuel to surge or pulse) fuel flow regulated down to 2.5-4 lbs. of pressure. Ideally you would have a quality regulator with a return outlet (sometimes referred to a PRV), Holley makes a very good one. If you want to upgrade your current pump, Carter makes a good electric pump that supplies around 5-6 psi. I have the part numbers for both if you need them.

 

[dennisonwj]

Could you please elaborate in why the electric fuel pump would be better than the mechanical specifically for the Weber (over the Cart original). The Weber was designed to replace the Carter in the Jeep and I thought is was the same specification. That it would be fully tolerant to the surge of mechanical fuel pump.

The other reason I want to go back to mechanical is "I do not want to remove the entire dash to fix the wiring underneath (hot wire of electric fuel pump going somewhere in the console ignition harness).

 

[PoliceMonkey161]

Could you please elaborate in why the electric fuel pump would be better than the mechanical specifically for the Weber (over the Cart original). The Weber was designed to replace the Carter in the Jeep and I thought is was the same specification. That it would be fully tolerant to the surge of mechanical fuel pump.

The other reason I want to go back to mechanical is "I do not want to remove the entire dash to fix the wiring underneath (hot wire of electric fuel pump going somewhere in the console ignition harness).

Well, I can try to elaborate but I'm on vacation and only packed my tablet so some of the tech sheets and links I'd normally include I don't have with me. The Weber you have is likely a 32/36 or a 38/38 which are both downdraft designs. The Weber you have was not designed specifically
for the 258, however they do lend themselves well to the Jeep motor. Some Weber suppliers (namely "Weber Carbs Direct") supply a kit (K551) which includes the adapter plates and linkage mods for the 258, but that is were the Jeep "specific" designs end. With that said, you have a great carb for your rig but it will require the proper installation to get you the performance that it is capable of.

Without going into great detail about the mechanical design of the downdraft Weber or it's history, it is very different from the OEM Carter or even the traditional replaces like Holley, Edlebrock or Rodchester. Unlike those, the Weber is open to the atmosphere prior to the ventrui's through an emulsion process (dual emulsion tubes or "E" tubes). All downdraft Webers rely on the 3 circuit fuel delivery process. Because of this, as a system, it only requires 2.5-4 psi feed. Higher fuel pressure will overcome the fuel float design and overfeed the 1st fuel circuit. The pulsing from a mechanical pump is not ideal because the diaphragm style pump provides to high of pressure and surges up and down with each stroke of the pump. I have seen may Webers installed with the OEM pump and they can work, but at the very minimum a fuel regulator is required. In the configuration using the OEM pump your only getting minimal performance and are hindering the inherent qualities that come with the Weber...... Many folks I have talked to are really working against the Weber carb, over thinking the install, trying to short-cut (making more work for themselves) and become dissatisfied with their purchase. In most cases its due to that they are familiar with the traditional carb systems and fail to fully research and understand the new setup that is required.

As for the under the dash wiring, not sure why the PO went that route? In the ideal setup, you would have the electric pump wired into a N/O / N/C combination oil pressure switch. Your electric feed would come from the distributor "hot" wire and the "start" terminal from the starter solenoid. This combined with the regulator, fuel filter and the properly installed return to tank line are optimal. One performance step future would be an HEI distributor. I have post a couple of threads discussing the proper wiring and plumbing but I can't pull them up with this tablet.

 

[dennisonwj]

I understand. Thank you very much for the post. Prior to reading this I spoke with technical support from Weber Carbs. They said......

He told me their carb. was engineered to work with the stock mechanical fuel pump. I think I have a Weber 34/36 DGEC. Need to check. He said in either case (mechanical or electrical), always put a Holley 12-804 Fuel Regulator between the pump and the carb. The regulator will "even out" the flow and the surges will be eliminated. Also, the Weber only takes 2.5-3 PSI, any more is too much.

TO clarify::: The PO has the hot wire going under the driver side dash somewhere. I need to look and see where. Right now the hot wire came loose, so I need to determine "WHERE" it was plugged in, it is fitted with a "blade" connector right now, so it slips into a harness somewhere.

Also, I need to determine if the Jeep has been "Nuttered". I will check tonight. I would leave it nuttered if it was. I just want to get back to some normal level to get a handle on "what" I have.

 

[jps4jeep]

Electric pump should be placed as close to the tank as possible to
1. keep the pump cool
2. presurize the line to reduce vapor lock.

 

[69jeepcj]

If the wire has a blade connector on it, it may have been stuck into a fuse in the fuse box for HOT. My electric fan is that way.

 

[8177]

Sorry to get to this party so late. If you want a mechanical pump to install as a baseline I have a practically new pump that might have 50 miles on it from Autozone. Its for an 81 CJ7 258. If it fits, you can check the numbers, send me your address and for the cost of shipping its yours. I installed a Fuel injection kit and this is just taking up realestate in the shop.

 

[superj]

It fits.

I had a weber 34/34 (Thats what yours is) and its not a great carb. A 32/36 and a 38/38 are great carbs but not the dog 34. The holley regulator works great though and I had previously used the same regulator on a BMW I had a weber on also. They do require very very low pressure so use the factory return line and you can get away with no regulator, I am set up like that now but have swapped to a holley a while ago because the 34 is a dog. And I am a huge weber carb fan.

I currently have a holley low pressure electric pump and no regulator but do utilize the fuel tank return which keeps fuel pressure perfect for the carbs. I have a holley regulator but took it off since I am using the return line