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Starting problem trouble shooting; What is my next step?
Topic Started: Mon Apr 17, 2017 4:42 pm (1,085 Views)
Mercedes29
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Hi all, I'm after some help on what the next steps are to identify my poor starting problem as its been going on for a while now.

The symptoms are that it takes a long time to start or requires pushing the gas pedal to get it going. The car seems to behave better when driven regularly, but the issue never completely goes away.

The ovp, cold start valve and fuel pump relay are working. The fuel filter is new as are the spark plugs.

This weekend, I removed the ke jet unit to inspect the rubber boot and clean the whole thing. Since putting the unit back in, the engine would start and then immediately die. I had to push down the plate on top of the unit as it was stuck - this solved the issue. It then died a few times when i took a for a quick drive when at low speed; twice at traffic lights and once at a roundabout. When i came back home, I sat with the engine idling at about 600rpm and it didn't die once.

I'm sure there are lots of reasons for my starting problem but I'm not sure what to look at next. Help would be much appreciated.
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stwat
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How have you tested the ovp?
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Mercedes29
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I borrowed a replacement that actually turned out to be faulty. Point being the engine ran terribly with the replacement so I concluded that mine was ok. Also, doesn't faulty OVP cause the ABS light to come one?
Edited by Mercedes29, Mon Apr 17, 2017 5:29 pm.
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optimusprime
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Yes pull it out anf give it a shake .If it makes a noise take the top off it and check the joints and look for tracking marks.
Do a check on all your fuses most are silver metal that corrode .
Replace with copper ones ,and when you do ,do it one at a time so you know from where the came from .
Then check all earth leads to the body, remove them and polish the body, refit with a little grease on them. These are all things to help you electrical system work better .After this your now looking at all the vacuum pipes around and on the engine. Come back after you have done it
Edited by optimusprime, Mon Apr 17, 2017 5:53 pm.
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246kharmadog
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Did you get to change that O-ring that you mentioned was suspect in a previous post?
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Mercedes29
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Yeh i changed the o ring.

-Optimusprime, thanks I'll go through these checks you mentioned. Any thoughts on the failed start and engine dyimg after putting the ke-jet back? There were no fuel leaks so definitely no issue on that front.
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Mercedes29
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Just a thought.. If I have an air leak, wouldn't the start up issue be consistent?. Sometimes it starts straight away without issue.
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JustbeCoz
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Needing gas pedal to start is usually an air leak issue. If the car is already warm or has been run recently then the air leak will not be such a big issue since less fuel is required anyway. pretty sure fuel pressure regulator requires vacuum to allow fuel through. Check the vac line connection to that as you may have dislodged/cracked the line or its connection when working around the ke system. You need to centre the afm plate to make sure it moves freely
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Mercedes29
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Yes i was just reading about the AFM plate. I understand there is a pin to reposition the height but how do you re-centre it?
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246kharmadog
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Mercedes29
Tue Apr 18, 2017 3:35 pm
Yes i was just reading about the AFM plate. I understand there is a pin to reposition the height but how do you re-centre it?
The instructions for centering the plate is the second pinned post in this section. It is a very informative post.
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optimusprime
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Put this in Google - Old Merc.net on there look down the left to -- K- jetronic fuel control unit on W102 engine cars Read it well ..
Edited by optimusprime, Tue Apr 18, 2017 6:15 pm.
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Mercedes29
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Cool thanks guys, I'll do some reading and get under the bonnet when i get a chance. Would a faulty distributor cap not yield similar symptoms? The general start up problem i mean, not the more recent kjet issue.
Edited by Mercedes29, Tue Apr 18, 2017 7:24 pm.
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Mercedes29
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246kharmadog
Tue Apr 18, 2017 5:53 pm
Mercedes29
Tue Apr 18, 2017 3:35 pm
Yes i was just reading about the AFM plate. I understand there is a pin to reposition the height but how do you re-centre it?
The instructions for centering the plate is the second pinned post in this section. It is a very informative post.
That's literally what I've been reading. It's like i was saying, it's adjusting the pin. Is that what you mean by re-centering?
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JustbeCoz
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Don't mess with the pin unless you have to. The afm disc is centred by loosening the small hex bolt in the centre of the plate and then inserting a feeler gauge around the edge of the plate to give a uniform gap. At that point you can re-tighten. Be careful not to overtighten it as it's small and doesn't need much. This should stop it sticking. Dizzy cap can affect starting but it's usually harder to start after a short period of running rather than easier which is your case. Always good to make sure normal items like Dizzy cap, rotor , spark plugs and air filter are good before moving to other stuff.
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Daveycooper
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Your symptons of hard start but generally ok when warm sound very similar to what mine were last year. Problem cured with new dizzy & rota. Fairly inexpensive. Do ht leads and spark plugs at same time. Its often the obvious stuff!
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Mercedes29
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The strange thing is that on a few occasions it has started instantly after sitting for a week which goes against the point earlier about it being easier to start when warm as less fuel is required.
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Mercedes29
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JustbeCoz - thanks ill recentre the plate to the correct position. Is the gap really so critical that it would cause the engine to cut out? I'm just wondering if there is something else at play that just happens to have coincided with removing the kjet.

I've also noticed that I'm unable to recreate the fault when the engine is just idling on my drive, it only cuts out when I've moved the car and then stop.
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optimusprime
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Did the engine ever run right? And just started to do this, or have you had the problem a long time. If it did run fine then adjustment to the throttle plate is not advised . Look at above post --plug leads spark plugs [the right type only] distributot cap and rotor ..Go for BERU parts , as bosch are noy up to specs just now .. And another thing to check for is vacuum leaks . And any fuel leaks at thev fuel distributor .
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optimusprime
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Clean out thev auxiliary air valve . It sits to the left of the distributor and is held in with a strap and 2 bolts ,you will see 2 rubber hoses from left and right and a electrical plug on the rear. Take it out but mind the hoses dont come of the engine side under the inlet manifold ,they are hard to get back in place .You can have leaks on these hoses that sit under the inlet manifold .When you have it off the car clean it out with white spirits shake it and let it sit for an hour or two .Then replace it and give it a try ..
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Mercedes29
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Optimus prime. There are two problems here, one is the engine cutting out at low idle which only started after the kjet was pulled so that definitely seems like the AFM plate.

The other issuing is sporadic starting which may be the dizzy cap. I will check the air valve now as well.
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Mercedes29
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I've adjusted the AFM plate which seems to have helped but the engine is still cutting it sometimes. I've also replaced the dizzy cap and arm as they were very corroded.
Before I look at anything else, could someone advise how to test the ovp relay with a multimeter. I've been reading around forums but am just finding contradictory info and broken links. I should point out my ABS warning light is not showing.
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optimusprime
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To many things going on . I would look at the electrics first plugs dist cap ht leads rotor arm ..And would never play with the mixture in the fuel distributor . And all parts fitted must be the same numbers of the ones removed , not one number off .
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Mercedes29
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I'm just looking at how to test the ovp as it's free and a simple procedure. The distributor cap and rotor arm are brand new.
Edited by Mercedes29, Sun Jun 11, 2017 10:05 am.
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JustbeCoz
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Ovp issues can be transient or intermittent which makes testing difficult. You can check the Electrical troubleshooting manual at the bottom of the page at this link.

Startek Manuals




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Mercedes29
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Thanks but the link is broken
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optimusprime
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Working for me [link ] /.I dont know a way to check out the OVP As this plays a big part in the electronic side . I can say,, its cost owners a few pounds in repairs, when this little box of tricks packs up .All other items are changed for no reason . Could you not try one from some one else .
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JustbeCoz
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The OVP is just a power supply relay so you can remove it and supply a stable voltage for testing purposes to the relevant pins in the relay connector socket by means of a separate 12v battery some lengths of wire and some male 4 mm bullet connectors.
If you can get a copy of the electrical troubleshooting manual from the link you will see a much more reasoned explanation of how and where to test using a multimeter, all the electrical engine and fuel management components.
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Mercedes29
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Hi All. Hoping someone can help as I'm really at a loss. The problems have been getting worse since my last post to the extent that the car is undriveable. It stalls when coming to a stop. It starts up again after a while but the time i have to wait for this is increasing. I fitted a new ovp today but no difference. I started it up after fitting the new relay then switched it off to reassemble everything in the engine bay- 15 mins later it wouldn't start; i waited 20 mins with no luck and called it day. It will probably start tomorrow as is the sporadic nature of this.

Things to note;

1. When i manage a successful start, idle goes over 1000rpm initially and then settles at 750.
2. Fuel pump always sounds when key is turned to first position.
3. Idle control valve seems in good shape. The valve opens with key at first position. When engine is off i can easily close the valve with a finger.
4. I cant find any cracks in the vaccuum hoses nor is there any hissing.
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optimusprime
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Now if it was me , then i would get a fuel pressure check on uper and lower chambers in the fuel distributor.
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griffin
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Get some spark plug testers.
The 4 red plastic ones from screwfix/Amazon for ten pounds.
Verify that you have a spark when it won't start -i.e. Verify they flash on and off as expected - or not if there is a problem..
Intermittent absent spark is likely to be ignition control unit... Forty quid for a new icu
If you want to check upstream of the icu. Make sure you have an ac voltage on the green lead pin. That will verify that the icu is getting a signal that it then amplifies.
When the icu starts going wrong it normally means it won't start occasionally, getting worse until things get unworkable.also idle starts getting gaps in it where it feels it will stall.
Edited by griffin, Thu Jul 6, 2017 10:11 pm.
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Mercedes29
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The spark plugs are really new so I'd be surprised if that's the issue. I'm not well versed in electronics so please bear with me. I can borrow a mulimeter and i know you can check things like voltage, continuity etc. but what do you mean by just 'make sure you have an AC voltage' ?
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griffin
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The spark plug testers don't just allow you to check spark plugs... They are like light bulbs in between your ignition leads and your spark plugs. They will allow you to see that your ignition system in general is working. They flash each time the spark plug is being sparked by the ignition system.
So when your car isn't starting, you can verify whether the ignition system is the cause of the problem by verifying if the spark plug testers are flashing. In the situation of not starting you need two people to do this test. One looking in the bonnet at the testers, the other starting the car. Also needs to be done when it's a bit dark.
If they don't flash when your car won't start, then, if you have a decent dizzy cap, plugs, etc, then suspect the ignition control unit.
This is what that unit looks like....
link
Edited by griffin, Fri Jul 7, 2017 6:20 am.
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Mercedes29
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Ok thanks and what did you mean by your AC voltage comment?
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optimusprime
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The idea is to single out the problem -is it electrical or fuel .You can look at the one and it turns out to be the other at fault . I think your fuel dustributor needs strip- down .But first get a pressure check on the system .Once done ,and checked out ,you then go to the electric side . On the distributor for the fuel have you a filter in the fuel line?
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griffin
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The AC voltage comment was related to testing the signal that is fed to the ignition control unit/module.

But first things first, check you are getting current to the spark plugs via the spark plug testers.

You will then know if you can rule out ignition problems - or that you have an ignition problem.

In my mind you have mentioned the problem is:-
a) Intermittent
b) The car wont start at all when its in the intermittent fail state

Electrical issues give this sort of behaviour, rather than mechanical (i.e. not fuel pressure, flow, etc.).

You've also stated that the Fuel Pump is always audible - so Fuel Pump Relay is unlikely..

The ignition control module, once it starts to go, will give intermittent no start behaviour... as you describe - but don't just buy a new one - check if the ignition is working via the spark plug testers

Rule out/in the ignition so you can move forward with your diagnosis



Edited by griffin, Fri Jul 7, 2017 1:06 pm.
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Mercedes29
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griffin
Fri Jul 7, 2017 1:06 pm
The AC voltage comment was related to testing the signal that is fed to the ignition control unit/module.

But first things first, check you are getting current to the spark plugs via the spark plug testers.

You will then know if you can rule out ignition problems - or that you have an ignition problem.

In my mind you have mentioned the problem is:-
a) Intermittent
b) The car wont start at all when its in the intermittent fail state

Electrical issues give this sort of behaviour, rather than mechanical (i.e. not fuel pressure, flow, etc.).

You've also stated that the Fuel Pump is always audible - so Fuel Pump Relay is unlikely..

The ignition control module, once it starts to go, will give intermittent no start behaviour... as you describe - but don't just buy a new one - check if the ignition is working via the spark plug testers

Rule out/in the ignition so you can move forward with your diagnosis



The car now doesn't start at all now, cranks but nothing else. I did the spark test and all the cylinders lit up. I also looked at the voltage regulator which had very worn pins; I've replaced it but no change. I also bridged the pins in the fuel pump relay connection but it still didn't start.

Can i now rule out the ignition as the problem?
Edited by Mercedes29, Sun Jul 9, 2017 4:31 pm.
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Mercedes29
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Update. The crank position sensor seems like possible cause but it is within the correct resistance range. I want to look at the throttle body sensor now, how can I test this?
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lowman
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have you checked the voltage that the afm potmeter sends out to the ecu?
this is supposed to induce approx 0.7 volts at idle.
Also..for preventative measures..i would replace the fuel pressure accumulator sitting on the same bracket as the fuel filter and fuel pump assembly.This is a neglected item,thats supposed to keep fuel pressure up to par in the system when doing hot starts .There is no replacment intervals,but it is suggested to be replaced everyother fuel filter change.
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Mercedes29
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CPS is faulty which makes sense given the symptoms. Has anyone removed one of these from a 2.6? Can you do this without lifting the car? It's on gravel with a slight gradient hence the question.
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MercManCraig
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It's located on the engine side of the bellhousing just by the oil filter housing bit tight but easy enough to change. When you do, don't forget to make sure the shim is in place when you put the new crank sensor in or you'll be buying two.
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