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Might I have the wrong injectors?

 
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Captain_Kirk  



Joined: 17 Dec 2009
Posts: 243
Location: Colbert, WA

PostPosted: Sun Sep 07, 2014 12:46 pm    Post subject: Might I have the wrong injectors? Reply with quote

In my quest to figure out why my car runs rich (little black smoke & stinky exhaust) I pull my injectors. I wasn't going to test them just check the number and replace them thinking they are old.
They have number 0437502008 on them. Nowhere can I find these are the correct injectors. Maybe this is my problem.
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1977 924na BlackSeaRD.com Torque Tube SuperBearings, Xenon air dam, 200# Weltmeister springs, Bursch header, 944 exhaust, Audi throttle body
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dacoma  



Joined: 26 Jun 2003
Posts: 3
Location: New Zealand

PostPosted: Sun Sep 07, 2014 7:13 pm    Post subject: Reply with quote

For model years 1976 to 1979 inclusive the fuel injectors are Bosch 0 437 502 013 (which have a female connector on the end for the banjo bolts on the braided fuel injector lines to screw into).

Starting in August 1979 (start of model year 1980-) the fuel injectors change to Bosch 0 437 502 015 (which have a male threaded connector for the screw caps on the metal fuel injector lines to screw onto).

It looks like 0 437 502 008 has the same female connector as 0 437 502 013, so it fits on your engine but might not have the correct features for the 924 fuel system like the right activation pressure or whatever. Best to get the proper injectors, at the very least it will eliminate one possible source of your trouble.

When I was troubleshooting & buying parts for my CIS system I found the Bosch website helpful for deriving part numbers from PET catalog: http://www.bosch-automotive-catalog.com/en/product-search
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Ian89C4  



Joined: 01 Apr 2011
Posts: 544
Location: North Carolina

PostPosted: Mon Sep 08, 2014 4:31 am    Post subject: Reply with quote

I went through this a while back as I had an 81 system with the hard lines going to the injectors. I could not get the system to enrichen, so I backdated to a 79 system (fuel dizzy and injectors).

The injectors are the same internally (pre and post 79) and open with the same amount of pressure. They also atomize the same amount of fuel depending on the pressure being sent from the fuel distributor which is controlled by the air plenum that pushes the plunger inside the fuel distributor up or allows it to come back down depending on the attitude of the throttle plate.

So your injectors are OK in regards to the part number.

What I would do is first do a spray test on all four injectors. The haynes manual has instructions for this but it is ridiculously easy if you have the injectors out already.

If they all atomize OK and are close to each other in fuel volume at the end of the 30 second test then the injectors themselves are OK.

I do however suspect that your issues do not lie in you injectors but in either the fuel distributor or warm up regulator.

You need to get a CIS pressure tester, fairly inexpensive and MUST with a CIS system. Without the pressure tester it will be impossible to diagnose the system. Once you get the pressure tester the haynes manual also have instructors for conducting the three pressure tests: hot, cold and system.

If the system is just running a little rich things are probably not too far off pressure wise and may just require a little adjusting. It is also possible that a prior owner played with the fuel mixture screw (DO NOT ADJUST IT IF YOU DON"T HAVE WO2 SENSOR as you will never get it right by sound or guessing).

I hope all works out for you.

Cheers,

Ian
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Ian Edgerly
Spiveys Corner, North Carolina

Current:
1981 924 Weissach Race Car ("Serenity")
1980ish 931 ("Alice")
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Captain_Kirk  



Joined: 17 Dec 2009
Posts: 243
Location: Colbert, WA

PostPosted: Mon Sep 08, 2014 3:43 pm    Post subject: Reply with quote

Thanks dacoma and Ian for your injector knowledge.
So I decieded to test them, maybe they aren't my problem. I pulled the middle two to check the part number, so now I pulled the front and rear and the rear injector was actually a ..013 part number. Hmmm maybe this is the culprit.
So I round up four glass jars that are exactly the same, get the injectors to spray and all mist really nice, no dribbles or dripping. So then I run them for about 30 seconds.
All four jars line up with the EXACT same amount, I mean you could not of poured the same amount into the jars and got them to line up the same.
So they are spraying the same, I measured it at 2 oz each (couldn't find anything in cc's).
Time to look elsewhere, the injectors are great, just going to replace rubber seal and leave them. Buddy at work (Saab mechanic) has a CIS pressure tester that I'll borrow, no WO2. Last autocross points race this weekend so I think I'll run it the same and dig into it when I can have it down for a bit.
Thanks again,
Captain
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1977 924na BlackSeaRD.com Torque Tube SuperBearings, Xenon air dam, 200# Weltmeister springs, Bursch header, 944 exhaust, Audi throttle body
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