hupp

My shark has been running very poorly lately - it will not rev over 2500rpm without sputtering and an almost complete loss of power. I've been busy troubleshooting the system and at this point I am trying to exhaust all options before replacing the fuel distributor. Today i checked for vacuum leaks by introducing compressed air into the manifold via the aux air valve outlet hose. Soapy water was used at vacuum fittings, gasket/seal areas, etc. and no vacuum leaks are evident. While doing this I did notice that my air sensor plate was not centered. So I adjusted and the shark runs better but not the problem is not completely solved. The air sensor plate is not perfectly centered but its pretty close (checked via feeler gages). How drastic are the effects of an uncentered air sensor plate? Does it have to be perfectly centered?

Sean79 5spd

Scott, I would think that centering of this plate would only affect idle but not othr driving conditions.


Sean

Rich9928p

Scott,

Do you know anyone that has a '78 or '79 928? If so, and you can convince them, by far the easiest way to confirm that your fuel distributor is bad is to "plug in" one that works. I was like you, I tore into EVERYTHING trying to eliminate the fuel distributor as the cause. When I "plugged in" a known good one, I was convinced.

SharkSkin

Scott, perfectly cenered would be ideal, but if it wasn't hangining up on the sides then the problem is definitely something else. There is a specific procedure in the WSM that you need to follow using a fuel injection gauge kit with the right fittings if you want to diagnose rather than shotgun the problem. Keep a LARGE fire extinguisher handy and be patient... these cars aren't that complex.

BTW, Rich also did a nice writeup on rebuilding the distributor. I've heard rumors that some vendors will not take your old distributor in as a core on a rebuild if you've opened it up. I don't know if it's true, but it might be worth double-checking before you dig in. I've been too lazy to follow up on it myself since mine is working great.

hupp

Thanks for the input guys.

Sean,

My idle did improve. The shark also starts much stronger.


Rich,

I'm almost convinced, but nobody around here has a spare distributor laying around.

Dave,

I've gone through the entire fuel system diagnosis. Many times, in fact, I think I can install the gages in record time now. Control pressures, system pressure and leak down all look good. Fuel delivery was also measured at the distributor outlet. This was what prompted me to replace my internal fuel pump (external is new as well). Delivery was 1150cc in 30s rather than the specified 1360cc in 30s. I thought that maybe this shortage was the issue.

I've also triple checked my timing via timing light and visual inspection of cam/crank/rotor orientation. I've checked the mechanical advence and vacuum retard function as well. Coil, wires, cap, resistors, rotor all new. All grounds have inspected and cleaned.

Also, I had a friend rev the shark until she started to miss. At this point I reached in and pressed down the sensor by hand. Result was the miss went away and the shark revved up.

GlenL

Maybe the mixture adjustment has shifted? That one Allen screw moves the entire mixture curve up/down. It is very sensitive.

SharkSkin

Could be an issue with the control piston(dist. rebuild time) and/or vac leaks where the u-shaped CIS housing halves bolt together. Sounds like you eliminated hoses as the cause, but how about that gasket?

hupp

Dave,

I sprayed the entire intake system down with soapy water (including the lower plenum) then blew compressed air into the plenum through the aux air valve outlet hose. No leaks were evident.

Glen,

I did not readjust the mixture, but my assumption is that this is not the issue. I'll re-adjust to check.

Dennis Wilson

Scott,

If you have taken the fuel distributor off, did you by chance reinstall the piston upside down? The teat goes down even though the upper chamber of the distributor has the same shape. Also, when moving the air sensor plate (engine off) is the resistance equal throughout? If not the cylinder/piston probably needs cleaning. BTW the air sensor plate being off center can affect the A/F mixture. Recommend you reset it.

Dennis

hupp

Dennis,

The distributor has been off; however, the piston was not removed from the housing. The teat is facing down. The resistance on the piston seems to be equal throughout but I must admit, I may not have noticed this issue. I'll check.

Ted K

hi dave!
can you tell me what and where the CIS housing halves are?? I have an idea but i'm not really sure. Maybe my 83 is different? Does it have a fuel distributor?
thanks in advance--Ted

SharkSkin

Hopefully this pic helps. Item 7 is the gasket between the two halves I was referring to.

Rich9928p

Ted,

I couldn't tell from your post what kind of '83 you have? If you have a US/North American 928, you do not have K-Jetronic CIS fuel injection. If you have an ROW "Euro" version then you do have a K-Jet system.

Ted K

a picture is worth a thousands words! I dont have that....mine is a US 928 and not a euro.
thanks for the info guys.
Ted