How do I test if a warm-up regulator is bad?

MikeyJ · 11-27-2008, 02:31 PM

My 1977 924 is having acceleration issues and wont go above 1000rpms. Its a really cold day here in colorado and the car started up and gave me acceleration for a bit. Once warmed a little the car started running rough again. I know I have a problem with ethier the regulator or the fuel distributor. I believe that my warm-up regulator might be bad. How do I test this? I dont want to run out and drop 100 bones to find out its actually the very expensive distributor.

924RACR · 05:18 AM

More likely it is the WUR (based on the symptoms you describe)... but the only way to know for sure is to use the proper fuel pressure tester to measure the control pressure. However, you do need the correct gauge, not just any pressure gauge - and they're fairly expensive. You need one specifically for testing CIS.

I recommend you pop over to the 924 board (www.924board.org) and see if there's anyone close by that might have one - I know we have a few guys in CO.

If not, you should be able to find (either through a search or just ask) the current best/cheapest source for a CIS pressure gauge. I think JC Whitless might have one now...

Yeah, actually they do, but it doesn't show the valve needed:
http://www.jcwhitney.com/autoparts/Product/Pr-p_Product.CATENTRY_ID:2008126/c-10101/Nty-1/p-2008126/Ntx-mode+matchallpartial/N-10101/tf-Browse/s-10101/Ntk-AllTextSearchGroup?Ntt=CIS+pressure+tester

You'd need I think the $60 one.

There should be a valve in there you can close to measure system pressure; looks like, as its delivered, it will only show control pressure (which is more likely to be the problem, if it's the WUR).

The test procedure is in the Haynes manual - you do have that, right?

914efi · 11-28-2008, 05:34 AM

Here's a ghetto test: Unhook heater wire from WUR and remove it from the engine so heat does not get to it, maybe wrap in a rag so it does not bounce around, fuel lines need to stay connected. If it is closing too tight and raising control pressure this will reduce or eliminate that from happening and the car will run different, maybe better but certainly different. This would at least tell you whether it is functioning even if improperly. Gauges will be needed to really know what is going on. Obviuosly do this carefully and only for the test.

If the car does not change, then the wur is not the major cause.

924RACR · 11-28-2008, 05:52 AM

Quite right - don't forget that it must be physically removed from the engine (which I overlooked first time I read this!), as it is warmed up either by the electrical connection or through the physical contact. By isolating it from both, you will keep it in the "cold" state longer.

Though eventually the car will warm up and the mixture may get too rich for the warm engine.

Also, realize that idle and mixture settings are to be set with the engine warmed up; another test will be to warm the car up, adjust mixture and idle there, then see if it'll still start when cold, and also how easily it restarts after shutdown while still warm.

Keep in mind also that when cold, the cold start valve is needed to get it to start easily. If wiring to these is bad, etc, it'll be hard to start cold.

Finally one more thing to not forget... if the car has only gas in it from when it was warm out... you may have a problem with water in your gas! It wouldn't hurt to put some gas-line antifreeze in it, if this is even remotely possible. Even better than generic gas line antifreeze would be Chevron Techron FI cleaner, which will capture any loose water but also help clean your fuel injection.