Replacement Warmup Regulator

[drivingfool]

I have a '73.5 911T 2.4 CIS car. My car has been running great for last five years, with the usual types of tweaks required to keep the engine running at peak. Recently, when starting the car after sitting for a few hours, it backfired and has backfired and run rough and bucked ever since. It stops backfiring at 3500 rpms and higher but has less power than before. It has a mild backfire at an idle. I've checked all of the simple things, plugs, wires, points, timing, popoff, all seem to be Ok. I enriched and leaned out the air/fuel mixture and there didn't seem to be any change in the backfiring. I originally thought that it may be due for a valve adjustment. Took it to a local mechanic who claimed to have experience with Porsches (I don't live anywhere close to a "porsche mechanic"). He checked fuel pressures (too high before the distributor and too low before the WUR) and screens(he found gunk) and felt that I needed both a new WUR and fuel distributor and was willing to charge me about $2600 to replace the parts. Thought that was a little steep and I can turn a bolt like the rest of you can. My question is 1) what are your opinions about the problem and 2)has anyone used the new style WUR that is now sold at Pelican Parts? Thanks

[boyt911sc]

Drivingfool,

Don't be foolish this time and be prudent in solving your CIS problem/s. Do you know what fuel pressures your mechanic obtained? If you're are inclined to do your troubleshooting, you need a CIS fuel pressure gauge. At this point, find out what were the control and system pressures your mechanic recorded.

I would suggest to test the fuel pump. Measure flow rate (liter per min.) if you don't have any pressure gauge to use. And keep us posted.

Tony

[slw911SC]

Fuel pump? Interrupted fuel flow and/or a failing fuel pump= backfires. Sometimes big ones!

[drivingfool]

Thanks guys, I'm going to do it myself this time around, I like a challenge. The fuel pump is a year old. I won't be going back to the mechanic as I don't know if he really knows what he is talking about. As I plan on keeping the car until I'm dead, I'll invest in a fuel pressure gauge. I started it a couple of hours ago, after putting some injector cleaner in it yesterday, and it started on "first pull" and ran pretty good until it started warming up, than ran rougher. I'll post again after I get some readings.

[T77911S]

you may have cracked the airbox when it backfired.