Injectors are not "vibrating" (3.2 motor doesn't fire)

bigpino · 05-25-2009, 01:49 PM

Did an engine drop for several oil leakage repairs and transmission revision. 4 years later after putting it back the motor cracks, but doesn't fire/start. I went through the troubleshoot list of the workshop manual and 2 things are not adding up:

1) Injectors are not vibrating. I've measured a block signal on the terminals, but no vibration noticeable with bare fingers or screwdriver on the top (next to electrics). How noticeable is it anyway? Is there an other way to check. At least one spark plug was wet of gasoline.

2) The resistance for both speed and reference sensors between terminal 1 and 3 is not measurable (my meter 20Mohm max). Spec's suggest >100Kohm though, but bigger than 20M is like not connected at all. Is this an issue?

Other things I couldn't check are:

1) Fuel pump pumps, but can't measure the pressure. A line was burst and I replaced it, so I assume the pressure is ok. Not sure about the residual pressure though.

2) Did not put speed/reference sensor signals on an O-scope.

3) Air flow sensor is provided with 4,6V instead of 5? Air temperature resistance is fine though.

4) Altitude switch, evaporation control, and airflow valve potentiometer not measured. Last 2, not sure how to.

5) Fuel is 4 years old. Could be too old.

Other guys think there is no compression (cracking is almost effortless) due to the extensive stand still. So they think we should tow and jump start in order to get the oil everywhere. We did not do that yet.

Any other suggestion to check?

Tyson Schmidt · 05-25-2009, 02:00 PM

Are the cluster grounds for the injectors properly attached to the intake manifold near the #1 intake runner?

dentist90 · dentist90's Garage

First time I put my motor back in it wouldn't start. Cranked just like it should but wouldn't fire, not even a sputter. Started checking everything systematically... spark, fuel pump, etc. I was so frustrated I could have cried.
Then as I started to take off the air meter housing I noticed that I had missed plugging in the 4 pin connector at the firewall. Turns out the car won't start without this!
Thought I'd mention it... just in case you've overlooked the obvious like I did.

bigpino · 05:48 PM

tyson, yes i attached that ground cluster. It is two sets of a couple brown wires.

dentist90, do you mean the aluminium air mass meter? mine has a 5 pins connector on lid side (facing to the back). Only 4 of the them are used. Is that the same connector? if so, there's only one way to plug it in. So how did you misplugged it?

rsscotty · 05-25-2009, 06:10 PM

I think the connector that dentist90 refers to is the 4 pin connector on the shock tower area on the left side looking in the engine bay. Easy to forget.

rick-l · 05-25-2009, 06:18 PM

Quote:

Originally Posted by bigpino

At least one spark plug was wet of gasoline.

Do you have a spark?

whiteSC59 · 05-25-2009, 06:24 PM

smell fuel. if it smells more like laquer than gas, dump and start over. usually fuel left over 1.5 yrs turns yellow and is better for thinning paint than starting an engine.

88-diamondblue · 05-25-2009, 07:10 PM

I did the same thing in forgetting to plug in the injection connection. The connector on he very right side of the picture next to the shock tower. I would also get rid of the old fuel and put a new fuel and fuel filter in.

dentist90 · dentist90's Garage

Quote:

Originally Posted by rsscotty

I think the connector that dentist90 refers to is the 4 pin connector on the shock tower area on the left side looking in the engine bay. .

That's the one. The harness (thick brown bundle with rectangular plug at end) can get under the weather strip at the firewall and gets lost and forgotten. Good luck.

bigpino · 06:59 AM

I got a very blue spark, Rick. And indeed the only harness connector "in front" of the engine was already connected. I can see how one can easily forgot.

I going to change the fuel, just to be sure whiteSC59.

Currently, my biggest concern are the injectors. No vibration what so ever in both key position "engine on" and during cranking. I expect it would vibrate during cranking. One guy suggested to put 12V directly on the injectors to see if they work. What do you guys think?

rick-l · 05-26-2009, 07:12 AM

Quote:

Originally Posted by bigpino

I got a very blue spark, Rick. And indeed the only harness connector "in front" of the engine was already connected. I can see how one can easily forgot.

I going to change the fuel, just to be sure whiteSC59.

Currently, my biggest concern are the injectors. No vibration what so ever in both key position "engine on" and during cranking. I expect it would vibrate during cranking. One guy suggested to put 12V directly on the injectors to see if they work. What do you guys think?

No

They are low impedance injectors and rely on the controller to reduce the current after they open.

Do you have any starting fluid to see if lack of fuel is the problem?

bigpino · 05-27-2009, 08:49 AM

Ok, no 12V on the injectors

. Sounds like current controlled instead of voltage. Anyway, we gonna replace of the fuel with fresh fuel. After that we going to tow and jump start it, just to get the oil all around the engine and hopefully it will build compression and start.

DW SD · 05-27-2009, 10:17 AM

injectors seem to get stuck closed after long durations of non - op. Why don't you check a few other threads. I think some have used 9V batteries or even some tapping to free up stuck injectors.
Can you cycle your fuel pump without cranking? I've used a jumper lead to run it. You will hear the fuel circulating and the fuel pressure regulator opening and closing. If you can check that off the list, you can focus on the injectors.

cranking will build oil pressure without towing, etc. That sounds dangerous, too.

Doug

bigpino · 05-27-2009, 11:13 AM

I can jump wire the fuel pump relay, I've done that before. I haven't notice pressure regulator doing its work though. How can you tell?

Having looked at the mechanic schematics, tapping the injectors seems too crude though in my opinion. Anyway, I will search the forum for stuck injectors in the mean while.

MURF · 05-27-2009, 11:30 AM

Injectors could be stuck..we use power probe to 12v one terminal and ground the other..just tap them no long term voltage..see if they click,...we have been very happy with
southbayfuelinjectors.com..try them cheap and fast turnaround..they send you flow chart of all the matched injectors

bigpino · 05-27-2009, 12:06 PM

Ok, just a quick 12V "brush" huh. With specs of 2-3ohms, it's quite a current . . . At least you say one can actually here them clicking.

It's hard to find a thread about solving stuck injectors other than replace them. If somebody happen to stumble upon it, please let me know. Just in case. southbayfuelinjectors.com has no porsche category, so don't know what the equivalent is. I believe I've got MFI (3.2).

bigpino · 05-27-2009, 12:35 PM

One more thing. How can one tell whether the fuel pressure regulator is working? Without a fuel pressure meter.

MURF · 05-27-2009, 05:13 PM

try removing the fuel rails with the injectors installed.bypass the dme relay to run the pump hot wire the injectors 1 at a time to check the spray pattern or you can remove the coil wires [disable ignition ]and check the spray pattern with engine cranking if you have no injector pulse this will be a waste of your time..did you try noid lite in the injector wiring harness plugs? we just finished 87 cab that sat for 9 years and we had s.b.f.injectors.check clean and flow equalize all the injectors $20 each..new seals pintales..look and work just like new....murf
ps install fi injector gauge between rail and regulator to check presssure

MURF · 05-27-2009, 05:17 PM

2nd thought..you can also upgrade your bosch injectors to the new series 3 style no metal inside..do not stick ever and have multiple port spray pattern for better partial throttle response...do a google search and check out new technology..murf

rick-l · 05-27-2009, 06:54 PM

Since you get a repetitive hot spark you know the speed and reference sensor are working. Now you need to know if the peak and hold circuit for the injectors is working. Without a o-scope the only way I know to check that is with a noid light (do a search for noid) or go to Radio Shack and buy an LED and a 50 ohm resistor.

One side of the injectors is at 12 volts and the other side is switched to ground in the DME to control them. They are all driven in parallel by one driver in the DME. You could also measure resistance across them because if one is shorted it disables all of them.