Pelican Parts Forums

Pelican Parts Forums (http://forums.pelicanparts.com/)
-   Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)
-   -   Motronic Injector Signal Testing (http://forums.pelicanparts.com/porsche-911-technical-forum/659459-motronic-injector-signal-testing.html)

rusnak 02-21-2012 08:26 AM

Feel for the second click in the dme relay (you changed it, right?), indicating that the dme sees the reference signal from the crankshaft sensor.

vreference 02-21-2012 09:47 AM

Quote:

Originally Posted by rusnak (Post 6572354)
Feel for the second click in the dme relay (you changed it, right?), indicating that the dme sees the reference signal from the crankshaft sensor.

I've not replaced the relay since it runs the fuel pump and DME very reliably (at least when not cranking... I've decided to take a closer look at power and ground today since I haven't done that lately) I did feel for a second click upon cranking and realized the clicking I'm hearing (that I thought was coming from the Ignition) is actually coming from the relay. Click once for every trigger of the reference sensor; although it's as though it's momentarily losing signal; a test light on the pump output stays lit despite the clicking. (I can never hear the pump running while cranking but I think that's more about how loud the starter is - the fuel rail is always pressurized after cranking.)

Tippy 02-21-2012 10:03 AM

This crap will drive you batty, hunh? :eek: :(

I can't wait to hear what you find. :)

rusnak 02-21-2012 12:17 PM

There is a reason for my question. You should only feel two clicks. Once when turning the key on, and a second while cranking. The second indicates that the DME is getting a signal from the crank position sensor.

I would get some starting fluid in aerosol form, and try it next. It sounds like you are getting spark (did you pull a spark plug and do a spark test)? It sounds like there is no reason for it not to run.

Please just put away the 'scope. It's time to get to more basic things. If it does not start with ether, then I would try it again with the cht grounded to eliminate that.

vreference 02-21-2012 01:18 PM

Well it was indeed very simple. I've used the #1 intake runner as a ground for lots of stuff but apparently not a big enough load to make it fail.

Bad #1 Runner intake ground.

*edit, let me add that I lovingly serviced that ground point and had it perfectly clean with dialectric grease even. It's the intake itself that wasn't grounded sufficiently. It was painted and I never cleaned anything off for any of the studs to ground too.

Tippy 02-21-2012 02:59 PM

So it runs fine?

vreference 02-21-2012 05:18 PM

Quote:

Originally Posted by Tippy (Post 6573178)
So it runs fine?

Yep. Lot of wasted effort but I'm quite a bit more familiar with Motronic now I suppose. I guess if I had been using a better meter I might have been tipped off, I was showing 0 ohms. Not sure how much amperage is being pulled through that intake... enough to float the ground I had anyway.

rusnak 02-21-2012 05:58 PM

Well that's just weird then...


All times are GMT -8. The time now is 04:53 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website


DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.