Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 924/944/968 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Aug 2019
Posts: 8
1985.5 starting problems

I have a 1985.5 944 with 24500 miles. The car is in fantastic condition but has been stored for 10yrs.

Took out of storage and flushed all fluids and replaced all filters including the fuel system. Replaced the plugs, battery, hoses and belts but did not touch the timing belt.

Replaced the fuel with new High Test and attempted to start. I got tach bounce but no attempt at firing. Cranking speed was normal. I put a small amount of fuel in each spark plug hole and car fired and ran until fuel was exhausted ( 2 sec approx).

Checked fuel pump quantity at fuel rail but not pressure...good flow!

Sprayed ether thru air intake and ran for moment.

Replaced the speed sensor and regulator and DME but no effect.

Any ideas!! Seems like a fuel issue to me but have voltage at injectors. Thanks!!

Old 08-28-2019, 02:37 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered
 
Join Date: Jul 2004
Location: Upstate New York
Posts: 2,423
The injectors may be stuck closed.

Try shocking them with a 9 volt battery and some jumpers. It might bring them back to life. If not, have them rebuilt at witch hunter, etc.
__________________
Good luck, George Beuselinck
www.944ecology.com
Porsche Deconstructor (tm)
We buy 944s and sell 944 parts (845-379-1944)
We rebuild torque tubes and instrument clusters for 944/968/928
Old 08-28-2019, 02:46 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Feb 2003
Location: SF East Bay
Posts: 1,855
If you've got fuel-flow out of end of rail, then test end back up chain. This test of final stage verifies everything upstream: battery, ignition-switch, DME-relay, DME, speed/ref-sensors, fuel-pump wires, fuel-pump, fuel-lines, fuel-filter, fuel-rail, FPR/dampener, injectors-wires, injector-power, injectors all at once!


1. Test end-of-chain to verify everything upstream is OK. Pull rail with injectors attached. Place little cups under each injector. Crank for 10-seconds. How much petrol did you collect? Are all injectors spraying identical amounts? If not, then move upstream one component at a time.

2. Test power to injectors. Disconnect all injector-connectors. Key ON, measure voltage at each terminal of every injector-connector. Should have full battery-voltage on one and zero voltage on other terminal. If you have any voltage on 2nd terminal, you've got wiring-harness issue with short. Power will flow across short instead of going to open injector.

3. Test DME pulses to injectors. Measure for injector-pulses at injector-connectors (oscilloscope best, otherwise 'noid-light will do). https://www.amazon.com/OEMTOOLS-27319-Piece-Noid-Light/dp/B01MZD76PK/

4. Measure fuel-pressure with and without vacuum hose attached. Bad FPR may not provide sufficient pressure even if fuel-pump is OK.


No need to waste time & money swapping out perfectly-working parts with brand-new perfectly-working parts and have nothing change. Measure and test parts to verify they are either good or bad before replacing them.

Last edited by DannoXYZ; 09-03-2019 at 03:07 PM..
Old 08-30-2019, 01:51 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
Join Date: Aug 2019
Posts: 8
Thanks Much!! This will keep me busy for a while. Will advise!
Old 09-03-2019, 05:14 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered
 
universeman's Avatar
 
Join Date: Oct 2014
Location: Lone Star State
Posts: 1,361
Garage
If injectors are stuck, sometimes knocking them on the ground firmly (not too hard) will unstick them. Learned this from witchhunter....
good luck
__________________
Jason - Austin, TX
82 911 SC targa (gone, but not forgotten)
92 968 coupe
Old 09-11-2019, 06:24 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Join Date: Aug 2019
Posts: 8
Thanks fellows! Sorry for the absense but had some health issues but now back at it.

I ran all the above tests and replaced the injectors but still no start, then I tried a test from Clarks Garage to test for a faulty FPR. I disconnected the electrical lead to one injector and attempted to start. Engine started and ran for several seconds until I shut down. I reconnected the injector and tried a restart but no success. Disconnected again and got a restart. Tried this several times and got restart each time. Engine runs a little rough on three cylinders but left run for 2-3 minutes. Tried reconnecting the injector while engine was running and stalled out immediately.

Thought I had problem solved so replaced the FPR. Tried a restart and nothing. Disconnected the injector and started immediately.

Running out of options only item not replaced is the Damper (FPD). Any ideas???
Old 10-21-2019, 07:53 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
Join Date: Feb 2003
Location: SF East Bay
Posts: 1,855
What fuel-pressure did you measure at rails?
With and without vacuum hose attached?
What did you measure for voltage at each injector connector for both terminals?

This is 5-minute fix once you’ve measured.
Old 10-21-2019, 08:53 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Aug 2019
Posts: 8
Fuel pressure at rail end without engine running (by-pass DME relay) is 2.4Bars or 40.2psi. My pressure gauge is has SAE fittings so had to clamp a hose line to adapt. Some slight fuel leakage so didn't want to start engine.

Voltage to each injector (both terminals) measured: 12.40/12.41; 12.41/12.41; 12.42/12.45; 12.42/12.42
Old 10-22-2019, 08:14 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
Join Date: Feb 2003
Location: SF East Bay
Posts: 1,855
Quote:
Originally Posted by jc944 View Post
Voltage to each injector (both terminals) measured: 12.40/12.41; 12.41/12.41; 12.42/12.45; 12.42/12.42
You have shorted injector harness. Should be 12.45/0 volts at each connector.

Somewhere, ground-wire coming from DME is connected to power-wire coming from firewall plug. This means injectors get zero current-flow when DME triggers them. Probably something like this somewhere with bare wires touching. Which is supported by randomly working when you wiggle injector connectors in process of plugging & unplugging.



Also, unless you bought brand-new injectors from Porsche dealer, they too need to be tested. Best to send them to http://mrinjector.us for cleaning. They will provide before & after test to show difference.

Last edited by DannoXYZ; 10-22-2019 at 08:58 PM..
Old 10-22-2019, 08:53 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
Join Date: Aug 2019
Posts: 8
Thanks, will trace out wiring to see if any breaks or roden chews. Will advise! Thanks!
Old 10-23-2019, 05:06 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
Join Date: Aug 2019
Posts: 8
Have traced down all injector wires and found no breaks or signs of shorting. Also disconnected injector grounds, cleaned, inspected and replaced. No Change.

Why does engine start and run when one injector is disconnected?
Old 10-30-2019, 05:32 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered
 
Join Date: Jul 2004
Location: Upstate New York
Posts: 2,423
I'm going to propose that your fuel pressure is too high.

The rationale is that the electronic drivers for the injectors cannot provide the amperage required to pulse all four injectors, but can provide enough current to pulse three of them.

Check the fuel pressure at the end of the fuel rail. You may end up replacing the fuel pressure regulator.
__________________
Good luck, George Beuselinck
www.944ecology.com
Porsche Deconstructor (tm)
We buy 944s and sell 944 parts (845-379-1944)
We rebuild torque tubes and instrument clusters for 944/968/928
Old 10-30-2019, 05:40 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered User
 
Join Date: Aug 2019
Posts: 8
Thought is was the FPR too so replaced but still no start on 4 injectors but does run on three. I reconnected the 4th injector while engine was running and shut down as if I turned the key off. Fuel pressure is at 2.4Bars or 40.2 psi which is within specs. Still looking for shorts but non so far.

Old 10-30-2019, 01:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 

Tags
starting problems 944


All times are GMT -8. The time now is 03:27 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2020 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

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