Slow to start when warm

[fla 9]

i fitted a check valve to my fuel pump but this didnt make any difference. Ive also used a new emulator and after a scan there were no error codes related to the immobiliser. so assuming the fuel is still in the line, it means there's no spark when its warm. I've changed the crank sensor too, but perhaps its worth checking the wiring TO the sensor?

So in summary ive done the following with no success:

1. new crank sensor (vw)

2. new blue temp sender (vw)

3. new emulator

4. check valve in fuel line on fuel pump

 

Welcome any other suggestions too..

[fla 9]

Trying to put some logic here:

If the car cranks but doesnt fire there is a combination of no spark or fuel in the engine. If we assume that the check valve in the fuel pump is holding pressure there shoukd be fuel in the line from the tank to the injectors. If it is not firing either there is now no spark or the injectors are not opening. If no spark, then either a fault at the coilpack side or crom fhe crank sensor causing the injectors and plugs to be 'immobile' If the crank sensor is new either it is not receiving the signal when warm (why?) or the lead to it is damaged.

In my case as i have obd2 i have used an emulator to defeat the car ecu immobiliser and use the external one. So a consideration for me was perhaps a faulty emulator. This is also replaced with a new one. In any case it does nog explain why it only occurs when warm. In my case its also after a short 5 minute run.

So i will be checking the.wiring to the crank sensor connector, the wiring to the injectors the wiring around thd coilpack. Other than that I'm totally stumped. Unless I've missed out something completely obvious...which is not unlikely!

[Jim Bowen 1]

Not really had much chance to check my warm starts since getting car back on road.

 

Am trying to think through why it does it. If its a problem with something heating up you'd expect some sign when driving.

[Dox 23]

How fast does the engine crank on the starter when hot, have you tried a cam sensor?

 

Other thoughts could be MAF or lambda, if the MAF is under reading air ingested it will under fuel too? If lambda senses over fuelling it will cut down fuel injected too?

 

Do you own a strobe light? Its easy to see a spark and quick to connect even when suited and booted

[fla 9]

Cranking is normal speed just takes about 10 or 11 turns before it fires. Ive got a new crank sensor so will try that. I also thought that the fuel pump relay was maybe having an issue of heat after running so dismantled it and removed the rocker to clean it properly. It too was basically clean. How would you use it to check for a spark?

 

I don't have a strobe unfortunately unless there's an app to use the phone light maybe?

[Dox 23]

Its a 4 stroke engine, so 2 complete rotations of the crank is just one rotation of the cam, the cam sensor is more accurate for timing than crank sensor (longer cranking if the cam sensor is faulty), does OBD2 use the same cam pick up on the cam as OBD1? The cam sensors are different OBD1 / OBD2?

[robrado974 1]

Not quite the same , but I've got my spluttering start back again . It's been fine for ages . First turn of the key it fires but the idle will not pick up . Turn the car off and restart and it's fine . No idea what causes it . The FPR is almost new , fuel pump is fine and the filter is fairly new . Still seems like it's not holding the fuel at the rail though ?. It's only on first start up, if you went on a drive and left it for a few hours it won't do it again , it starts fine .

Edited June 24, 2017 by robrado974

[fla 9]

Dox I'll swop out the cam sensor and see how it goes - obd1 and 2 have the same one

 

Rob - put in a check valve in the fuel line by the fuel pump. Might help. If you send me your address I'll pop one in the post to you as I've got a spare

[Dox 23]

Does the pump not prime when starting from hot? Why the need for a check valve then?

[robrado974 1]

Dox I'll swop out the cam sensor and see how it goes - obd1 and 2 have the same one

 

Rob - put in a check valve in the fuel line by the fuel pump. Might help. If you send me your address I'll pop one in the post to you as I've got a spare

Thanks Hasan . I'm going to do some checks on the other valves . If they are fine , I will take you up on your offer mate .

Thank you .

[fla 9]

Dox looks like you were on the money there. New vw cam sensor i bought about 5 years back seems to have improved the warm start, although ive only taken it on two runs so far. Will see how things pan out over the next week or so. Strange that nothing came up on vcds though?

[fla 9]

Well that didn't last long - very long cranking again this afternoon. Now I have absolutely no idea what the issue is..

 

So a quick summary:

New crank sensor

New cam sensor

Fuel pump relay checked and cleaned

Error codes checked deleted and rescanned

Check valve in fuel line

New blue temp sensor

New immobiliser emulator

Edited July 4, 2017 by fla

[fla 9]

what i find works is to turn it over once for maybe 4-5 cranks, stop, turn off and then start again. Then it fires in 2-3 turns instead of about 16 normally. This to me suggests a fuelling issue - ive got a new fpr which i'll change just to rule it out but i would have thought that the check valve in the fuel feed line would have this sorted. Unless the fuel pump itself is faulty when it gets warm.

[Cacokicksass 10]

I've a different heat related issue with my 1990 16V, but similar symptoms.

 

When the car has been running for a while and the engine is warm, car won't even turn over, let alone attempt to crank.

 

I had to get the head skimmed recently as the engine was getting extremely warm, didn't take long to figure out what the problem was and after this was done took the car for a good long spin that weekend, and after stopping for a few minutes at a shop car started straight away, so assumed problem sorted.

 

Was picking the young lad up from school the other day and was sitting in traffic and could smell the heat from the engine, sure enough, when I went to start the car same problem. After about 15 minutes, car started as if there was never an issue.

 

I've been told by a mechanic friend that there is no crank sensor in these cars, any alternative input would be great.

[1200 bandit 10]

I had this on my 2.0 16 V ,lots of engine cranking battery going flat,fitted new battery sill the same when the engine its starts runs ok

After checking l found that the wiring to the engine temperature sensor had fell off inside the rubber boot that covers the wiring After carried out the wiring repair starts when hot

Note the engine did start form hot then next time whoud not start from hot

Edited September 3, 2017 by 1200 bandit

[Cacokicksass 10]

I had this on my 2.0 16 V ,lots of engine cranking battery going flat,fitted new battery sill the same when the engine its starts runs ok

After checking l found that the wiring to the engine temperature sensor had fell off inside the rubber boot that covers the wiring After carried out the wiring repair starts when hot

Note the engine did start form hot then next time whoud not start from hot

 

Cheers bandit, I'll check that, the car is over 27 years old and I already had to rewire the headlamps because of corroded cable crimps. Problem I'm having is that the engine won't even attempt to crank which I would assume to be more a symptom of a crank sensor, but if the car doesn't have one that can't be it.

[Cacokicksass 10]

[ATTACH=CONFIG]88724[/ATTACH]

 

Not sure if you can blow up this snip, but seems fairly basic, I'm not even getting a crank when the engine is warm and can't see any sort of temp/position sensor in series with the ignition and starter motor, so maybe it is corroded cables or connectors.

Edited September 3, 2017 by Cacokicksass

[1200 bandit 10]

Sorry l was reply to fla post

On your Corrado fist check the battery out.then check thr leads to the body,engine,battery are clean and in good condition and secure

Check that no leads,starter motor are getting hot when the engine is cracked when hot

Check feeds to the stater motor 12 volt on trigger wire when engine cranked

12 volt on the main lead and about 10.8 volt on cranking.

If all checks out remove the starter motor and get it check out

Hope this is some help to you

[fla 9]

since fitting the schrick I also replaced the leads, new spark plugs and most importantly a new fpr (from ebay, not genuine). Getting used to the schrick (which is a great mod!) but the new fpr seems to have solved the long cranking issue, although i cant quite understand how, especially as i've also fitted a check valve in the fuel tank too. Its a 4 bar regulator, iirc

[Jim Bowen 1]

I've noticed now that mine still has weird hot start issues, starts ok, but the revs climb really slowly as if its starting at 100rpm and slowly raises until idling properly, not kicking into life straight away if that makes sense.

[seanl82 23]

Do you have a link to the one you bought Hasan?

[fla 9]

here you go sean:

 

https://www.ebay.co.uk/itm/FUEL-PRESSURE-REGULATOR-VW-AUDI-SEAT-SKODA-1-6-1-8-2-0-2-9-1-8T-VR6-VR5-4-BAR-/281018928856?hash=item416e088ed8

 

Hope it doesnt give any issues further down the line! Its only been about 50 miles since i fitted it.

[seanl82 23]

Thanks mate. For that price it's worth a shot!

[_Matt_ 32]

I've bought one too and why not at that price! I have a similar issue - starts fine cold and immediately restarts fine when hot. Leave it for 5mins and it'll crank 10+ times and then fire up.

 

I've also bought a new coil pack (car is a rough idle and miss fires a little) in attempt to resolve so will fit these separately and see what happens.

[robrado974 1]

I’ve replaced the FPR , new filter and a second hand pump a while back. Every now and again I still get a spluttery start from cold. The revs fail to pick up .Second crank it will fire straight away . Still think it’s a fuel problem. Maybe the second hand pump is on its way out ?.