fuel pump conversion questions Options

[Scott-thundercat]

hey didnt see this one when i searched- is it possible to use a different fuel pump for our car? i have a pump out of a mercedes 190E. its fuel pressure is 85 lbs. i was wondering- since our regulator would keep it at 34 or whatever- cant i use this one as the excess will just flow to the return on the tank? i'm asking cause i have it sitting here and it would be easy to make it work assuming i wouldnt destroy the fuel system in the car...

[aveale]

Yes for sure.

As long as it meets pressure and volume and voltage requirments.

T

[Scott-thundercat]

so it just has to meet the minimum flow and pressure requirements? this one flows enough for a 135 hp 2.3 liter so it should be fine for a 1.7 85 hp engine... i'll see if it works. what doe i do with the fuel line that splits into the pump? just do one in and one out? i'm guessing that extra one is to deal with vapor lock...

[Cap'n Krusty]

You may not yet know me, Scott, but I'm sure you'll become familiar with my attitude "problem" sooner or later. I've spent the last 33 years as a professional German car technician and shop owner.

That said, here's my answer to your question. DON'T DO IT. The regulator isn't made to deal with pressures well over 100PSI, and with the kind of flow rate the MB pump has. Sooner or later, there's gonna be a problem. Furthermore, I sell a lot more of those than I do the 914 pumps, 'cause they go bad all the time.

If you want to convert to a "more modern" design, use the pump made for VW bugs/busses/vanagons and 75-76 914s. Just replace the "Y" fitting in the return line with a straight tube and be done with it. You'll also have to use the later filter and a short piece of 12 mm fuel hose, but that's generally not a problem as they're readily available. BTW, you'll notice I called that setup a "return line". It's not a mechanism for preventing "vapor lock", it's a bleed off of excess fuel pressure at the pump (released by the check valve on the pump itself).

The Cap'n

[ClayPerrine]

(IMG:style_emoticons/default/agree.gif)


The Cap'n and I agree on most things. He is very knowledgeable about these cars. You can do it right, or you can choose to be the DAPO for the next owner.....

[Scott-thundercat]

yeah those pumps do go bad a hell of a lot! hence why i have 2- i actually got em off the 300E (slightly different than the 190E) which comes with 2 pumps... used one on the car and kept the other for when it went bad again!

basically i'm just looking for something cheap and quickly purchaseable- so i can get this car on the road... i wouldnt do a hack job replacing the pump- i'd get some brass fittings to fit it so i could just hook it in place... where's a good place to find the other pumps? i just saw kragen wants 150 bucks. im looking for like... 50. so i think i might use this pump for a while unless i luck out at pick and pull... how much would you charge for a used one? the correct one?

Thanks for the advice- yeah i've read a lot of your posts- seems you know your way around the wrench...

[Scott-thundercat]

so anyhow i tested the old pump- nothing. i hooked up all the fuel lines- put on a new filter where the old one was- unhooked my vice grips (well one of em came undone (on what the PO had hooked up as the return line- and fuel comes gushin out- i'm like okay whatever- put the new line before tooooo much came out). when i unhooked the vice grip holding the line that had the filter on it- no fuel came out.... at which point i realized the PO had them hooked up the wrong way... so after all that then i have to switch the feed and return lines. but the merc pump fits in there decently. as soon as i find a porsche pump i'll put it in- i made some connectors up to fit onto the factory plug so i wouldnt ruin it.

very frustrating after spilling fuel all over me to find they were backwards! but the new pump turns on. yay! now to fix it tommorow.