Sad day......... Fuel pump not working
- Thread starter 944 man
- Start date
If you have a look at http://www.clarks-garage.com/ there's a 'garage shop manual' link. On this page is a troubleshooting section covering most 'engine won't start' scenarios.
Apologies if you've already seen this, but I've found it immensely helpful and allows you to work through a methodical checklist of checks.
Good luck with it.
Apologies if you've already seen this, but I've found it immensely helpful and allows you to work through a methodical checklist of checks.
Good luck with it.
peanut
Active member
944Volks said:Okay replaced DME relay with genuine part.
New battery fully charged.
Cranking. ..nothing! []
Tacho was bouncing all over the place.
What can it be?
Any good USA tech forums?
Come on guys!
this is not a simple engine to troubleshoot even when you are stood in front of it let alone when you're trying to do it blind on the internet from a distance with a very sketchy non specific description
Many cars have been abandoned or sold on because of hard starting and erratic running issues that could never be solved.
The Bosch fuel injection and ignition management system is a complex bit of kit and needs checking and testing in a methodical and systematic order or you'll just end up doing what everyone else does . Buy and fit one new part after the other until hopefully it starts to work again. Or you run out of patience
Or you could Put it into a local garage and watch them replace everything at random until they give up or you run out of money.
Start by isolating and testing the basics .
Forget buying a new DME relay just make a simple 3x wire bypass as described on Clarks garage.or Pelican
The 3 wire bypass does what it says on the tin. it forces the pump to run permanently even with the ignition off so you know you have a fuel supply .
It also provides a permanent supply to the second relay and to the ECU so it effectively bypasses the entire DME relay .
Make sure that you are getting sufficient fuel pressure at the rail and injectors by fitting a pressure guage to the fuel rail with a piece of garden hose and a jubilee clip.You don't need to spend a fortune there are plenty of cheap fuel pressure kits on ebay.
Test that you are getting 3.0 Bar pressure when cranking and then do a leak down test to make sure that the fuel system is holding fuel pressure for at least 20 minutes or so.
Now that you've tested the fuel delivery system start testing the ignition system.
The 3lt engine from the Turbo and S2 cars uses ignition modules to boost the ignition pulse from the ECU like this http://www.ebay.co.uk/itm/Porsche-911-3-6-928-4-7-5-0-5-4-944-2-5-2-7-3-0-Ignition-Module-92860270601-New-/401201616412?hash=item5d697ad61c:g:gykAAOxycmBS2TXQ
Test the ignition module and work your way forward to the spark plugs
Heres a good troubleshoot from pelican garage which includes a description of how to fit a 3x wire bypass to the DME relay socket for testing purposes
944Volks
New member
Okay.
Borrowed an old gauge.
Dug out some old rubber fuel line and 2 hose clips.
Bypassed DME relay.
Pump ran up to 4bar and holding.
Discount.
After 3 minutes it dropped to 3bar.
After 10 minutes was at 2bar.
So fuel looks good. Reckon it's just not getting spark.
Where do I go next?
Sorry Clarkes link isn't working for me.
Borrowed an old gauge.
Dug out some old rubber fuel line and 2 hose clips.
Bypassed DME relay.
Pump ran up to 4bar and holding.
Discount.
After 3 minutes it dropped to 3bar.
After 10 minutes was at 2bar.
So fuel looks good. Reckon it's just not getting spark.
Where do I go next?
Sorry Clarkes link isn't working for me.
peanut
Active member
thats excellent work well done. you've eliminated the pump, non return valve and FPR and verified that the fuel system is holding pressure for restarts thats good progress.
The 3 wire bypass will be bypassing both DME relays so your ECU will be powered up so if you have no spark the next step i to check the ignition module . There should be a test proceedure on the forum somewhere but if not Parrogon garage should have something. If the ignition module checks out ok and its being pulsed by the ECU then its just a case of checking the Hi tension components forward - coil -distributor -rotor -leads -plugs
This whole issue could simply be down to poor electrical connections which was aggravated by your engine wash .
It would not hurt to clean all connections to and from the coil . i usually file the edge of the rotor and the 4x brass contacts in the distributor and the edge of the spark plug electrodes etc . Electricity likes nice clean sharp edges to arc to and from.It all helps.
Lastly you should probably clean all your earthing points particulary the strap top of the block at the back of the firewall. An easy way to check your chassis to engine ground is run a battery jump lead between the battery negative terminal to a clean earth point on the engine somewhere.
One more check . Check the connector to the ECU hasn't got damp
The 3 wire bypass will be bypassing both DME relays so your ECU will be powered up so if you have no spark the next step i to check the ignition module . There should be a test proceedure on the forum somewhere but if not Parrogon garage should have something. If the ignition module checks out ok and its being pulsed by the ECU then its just a case of checking the Hi tension components forward - coil -distributor -rotor -leads -plugs
This whole issue could simply be down to poor electrical connections which was aggravated by your engine wash .
It would not hurt to clean all connections to and from the coil . i usually file the edge of the rotor and the 4x brass contacts in the distributor and the edge of the spark plug electrodes etc . Electricity likes nice clean sharp edges to arc to and from.It all helps.
Lastly you should probably clean all your earthing points particulary the strap top of the block at the back of the firewall. An easy way to check your chassis to engine ground is run a battery jump lead between the battery negative terminal to a clean earth point on the engine somewhere.
One more check . Check the connector to the ECU hasn't got damp
graham tompkins
New member
Hi Karl,, I have followed this post for a while and the advice you have had, albeit sound, your post of 7th August ! You jetwashed the engine?
It may or may not be a shock to you but car electrics and water, particularly under pressure, are not good bedfellows... it's a real no no, and not wishing to be harsh, is a really stupid thing to do.if youd left it 10 days it may have been ok, but 10 minutes? There are numerous electrical connections, plugs etc and the conductivity of water will cause havoc. My advice is work back checking all plugs, replace the dizzy cap and ht leads, blah blah blah and use a moisture repellant as Vitesse has said.
hope it gets sorted soon
regards
Graham
It may or may not be a shock to you but car electrics and water, particularly under pressure, are not good bedfellows... it's a real no no, and not wishing to be harsh, is a really stupid thing to do.if youd left it 10 days it may have been ok, but 10 minutes? There are numerous electrical connections, plugs etc and the conductivity of water will cause havoc. My advice is work back checking all plugs, replace the dizzy cap and ht leads, blah blah blah and use a moisture repellant as Vitesse has said.
hope it gets sorted soon
regards
Graham
graham tompkins
New member
Dreadfully sorry Karl, didn't realise, and not at all apparent from your posts that you were a seasoned expert...my mistake.
vitesse
Active member
Agree,Graham.
I have 2 types of timing strobe light-one type connects between a chosen detached plug lead & the plug itself & is an easy way to see whether there's HT at the plug because the strobe either flashes or not when cranking the engine.
I also use one of those Lucas orange spark indicators which you can place at a plug or at the coil to give a visual indication as you crank the engine
Much safer given the HT involved than holding a plug against the engine.
I also use a simple test lamp having crocodile clip equipped leads which can be put in series in the coil primary circuit & should flash if LT is present as you crank the engine.
As you say Karl,most frustrating when it drove in but now won't drive out.A continuity tester have long leads could also be a help just in case an important ignition feed wire has developed a break ( which can happen) which is why I also have a long wire again fitted with crocodile clips each end ( but using Lucars as well ) so that feed wires can be temporarily be bridged.
I have 2 types of timing strobe light-one type connects between a chosen detached plug lead & the plug itself & is an easy way to see whether there's HT at the plug because the strobe either flashes or not when cranking the engine.
I also use one of those Lucas orange spark indicators which you can place at a plug or at the coil to give a visual indication as you crank the engine
Much safer given the HT involved than holding a plug against the engine.
I also use a simple test lamp having crocodile clip equipped leads which can be put in series in the coil primary circuit & should flash if LT is present as you crank the engine.
As you say Karl,most frustrating when it drove in but now won't drive out.A continuity tester have long leads could also be a help just in case an important ignition feed wire has developed a break ( which can happen) which is why I also have a long wire again fitted with crocodile clips each end ( but using Lucars as well ) so that feed wires can be temporarily be bridged.
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