Fuel Filter Woes

[Jol Dantzig]

Perfect summer day blemished by roadside breakdown!

It was a perfect Porsche day. Cool air temps, sunny skies... let's GO!
Got about ten miles or less in when the motor started losing power. Full throttle romps while at speed produced almost no acelleration. Finally it died at a stop light, and would not re-fire.

The motor turned over as normal, but it just would not catch. A scan of gauges and under the lid turned up nothing unusual.

As time went on, the motor would start, and run for a few seconds, then die. The longer I waited, the longer the motor would run before dying. It still would not rev when given any boot.

After about 50 minutes it started and could rev... I was 3 miles from home so I kept the revs up and made sure not to stop for any lights etc. (hey, it was an emergency) and made it home no worries.

I'm new to the MFI so I'm looking for a little direction here. It seems like a fuel delivery problem to me. What do you guys think?

I've read the threads previously about fuel filter/fuel "crud" problems, so I think that I'm on the right track here. My question is simple, do the S and RS share the same (engine compartment) fuel filter?

Also, as long as I'm at it how about the ignition components? How much was carried over intact to the RS? Rotor, cap etc?

[pwd72s]

Jol, Seems to me you may need to check out the entire fuel system. There is a brass screen in the tank that can become plugged with rust flakes from the inside of the tank...some people place an aftermarket filter downstream of that. Then there is the MFI filter itself...I do believe they are the same for both S and RS. Now available only as a Porsche part #110.909.10. For around (gulp) $60 each. I used my last $100 PCA discount coupon to stockpile four of them. The RS distributor is slightly different than the S distributor, and the S distributors varied from year to year, tho I'm not sure of the numbers breakdown. I recently went to an RS distributor on my '72S, and noticed an improvement in bottom end. Do you know whether your problem was spark or fuel? A friend who recently had a CD box fail told me it was a sporadic failure...car would run, then die, then run again...Frankly, I'd probably (me personally) want to go for a professional diagnosis before starting to replace things willy-nilly.

[neilk]

Get rid of that unreliable MFI, I have a set of functioning Webers that I can trade with you.

[Jol Dantzig]

Neil,
Why didn't I think of that myself? Actually, I should just pull the whole motor out and put in a nice 3.6 with modern FI. Hahahaha.

I'll be diving into it later this week... got to solve this before Lime Rock.

Jol

[RickS]

'73s didn't have fuel filters, but I am interested in adding one just as an ounce of prevention. Where is recommended? Thanks

[RickS]

Oops - forgot to ask for a part number? Do I need to go strictly Porsche or is there a lower cost alternative?

[Chuck Miller]

Rick,

Not completely sure of your question…

In your title it says 73-S 2.7RS spec motor … if that's the case then your MFI requires a VERY elaborate fuel filtering
System … It's the big silver spin-on canister with all the hoses and wires coming into and out of between the CD box and the left engine cover hinge.

Also, the stock gas tanks have a filtering 'sock' at the exit…

If you want to add an 'inline' fuel filter between the tank and the pump, or between the pump and the MFI filter I guess you can … but… I haven't seen it done very often on a street car.

Hope this helps,

[pwd72s]

I've heard of it done Chuck, just an aftermarket inline filter, chevy, ford, whatever...past the sock up front, can be installed under the easily unbolted pan...dunno if it's a big plus tho, just a bit of added insurance...less expensive than the MFI filter, and easily replaced.

[neilk]

Speaking of fuel filters, are the fuel hoses off the filter braided cloth type or plain?

Can someone post a picture of the fuel filter assembly with hoses attached? I'd like to make sure that my hoses weren't rerouted to bypass the filter and go straight to the <gasp> carbs.

Thanks

[pwd72s]

CARBS??? '73 S cars should have MFI! Since Tom's car is running ITG air filters, I'll post a pic of his MFI engine, to give you a view of the injection stacks, the injection pump