Could mixture be too rich because of bad injection valve? Options

[velum]

Hi!

I am at lost with my '73 914-4 2.0L FI system... (IMG:style_emoticons/default/wacko.gif) I changed the MPS and calibrated the new one based on the old one (because it was from a 1.7L engine. The old one leaked a bit too much), I changed the wire harness, and I changed injection valve seals, but my engine is not running properly... it sounds irregular a bit like a 2 stoke engine... maybe my engine is running only on 3 cylinders... But my four spark plugs are completely black, so I conclude that the mixture is too rich. I was gonna check my injection valve, but then I started wondering whether a bad injection valve could cause the 4 spark plugs to be black... I don't think so, but I am asking. I played with my MPS inner adjustment screw, and I could get the engine to run a bit better (ie to sound less like it is gonna stall), but then I measured the number of Henrys the coil is giving me, and it way off what I assumed it should be.

My main question here is whether the injection valves could be at fault. And I would like to know if you have any suggestion about what to test next.

Cheers!

JF

[swl]

It it were me there are two places I would check. First is the CHT. My experience with them says they gain resistance with age. That equates to rich running. The other thing I would do is check the spray pattern on the injectors. Sending them out for cleaning is always a good thing. There are a couple of places in the states that have a good reputation but you should be able to find injection service in Montreal.

I've never messed with the MPS. Always thought the MPS had to be the correct one for the ECU. Brad Anders site will give you details on that - he has done some pretty impressive research.

[Bleyseng]

Black plugs usually mean the CHT is bad as you are going way too rich! Test it with a ohm meter to see.

Now that you have screwed up the calibrations of your MPS you will first have to get it running half way correctly before messing with the MPS to reset the AFR. Go thru everything to make sure its correct- adjust the valves, check all the vacuum hoses, have the injectors cleaned and re installed with new seals, new points etc....
Since you have a 73 2.0L make sure you have the correct matching FI parts- 017 CHT, 270 Ohm ballast resistor, 037 MPS, green injectors etc....

[orange914]

i'm no expert, but the d-jet site list different mps between the 1973 1.7 and 2.0, even though the ecu is the same.
http://members.rennlist.com/pbanders/DjetParts.htm


BTW is injector valve refered to the fuel injectors or the cold start valve? henry's ??

[realred914]

you recalibrated a 1.7 mps to match a 2.0 mps and your lost with a FI system? Thats quit a big undertaking for someone even framilar with the Fi system much less for some one lost.
at anyrate:
I would suspect it could be many things, maybe assure yourself the mps is calibrated ok, the head temp sendor as stated has to be right else the car may run way too rich (or too lean depending on failure mode) be sure to wiggle the head temp wire vigurasly when ohm testing to check to intermittant shorts/breaks.

the trigger points could be worn and bouncing giving double pulses of fule (way too rich) also so that needs to be checks for wear.

any bad intermittant wires could be a probelm too

the cold start injector could be shorted on or leaking.

airfilter clogged?

also badly adjusted valves, or bad timing can cuase poor running too make sure basics are good also.

[Mark Henry]

.... but then I measured the number of Henrys the coil is giving me, and it way off....

Some Henry's are always a bit off (IMG:style_emoticons/default/biggrin.gif)

[velum]

Hi!

Thanks for pointing out the CHT Sensor. I think this may be the culprit.

I have read the pages written by Paul Banders quite a few times by now, and yes this is a goldmine of information for anybody with a fuel injection 914.

realred914, you were right.... one should wiggle the CHT sensor wire when testing it. I could get all kinds of readings by doing that... I had tested all the ECU connector terminals recently (cf table under point 10 on http://members.rennlist.com/pbanders/DJetParts.htm), and everything looked fine. This is what got me confused. I did not suspect the CHT sensor to be wrong.

Now I guess, I will have a fun time finding a new CHT sensor for a '73 914 2.0L (part #0 280 130 017). I have a spare 0 280 130 012 that Automobile Atlanta sold me in replacement for the 0 280 130 017. However, according to all my reading, this may not be a good idea to replace a ...017 by a ...012 CHT sensor. They don't have the same resistance at the same temperature.

For people who were wondering what Henrys are, they are the units used to measure inductance: http://en.wikipedia.org/wiki/Henry_%28unit%29

Cheers!

JF

[swl]

You might want to find someone with a known good 2.0 MPS to compare with your efforts to recalibrate the 1.7. There are a few 2.0s in the Montreal area.

There have been lots of good discussions about the 2.0 CHT but I can't seem to make the search engine find them.

[Bleyseng]

Do you have a Wavetek inductance meter? If so I can give you the readings to reset it to factory settings..

[velum]

Do you have a Wavetek inductance meter? If so I can give you the readings to reset it to factory settings..

My multimeter is an MTP 2325, not a Wavetek. However, I would still be curious to compare my measurements with yours. Here are mine taken from my car's original MPS.. I used these values to calibrate another MPS taken from a 1.7 L 914:

http://www.beauchamp.me/914/MPS0280100037.htm

I am located in Montréal at around 180 meters (590') of altitude, so not that much above sea level.

Cheers!

JF

[velum]

Yeap! It was the CHT sensor. (IMG:style_emoticons/default/piratenanner.gif) Thanks guys for putting me on the right track!

JF