Struggling to start when warm

Hello all,
I'm having an issue starting my mk1 when it's warmed up. The car starts well when cold but I need to pump the accelerator a fair bit to start it from warm. If I forget to pump the accelerator when it's warm it can be a nightmare to get going again and can cause backfires with flames shooting out of the exhaust. I changed the fuel filter last year which had no effect. Wondering if it might be the fuel pressure regulator?
The car runs really well other than this starting issue.

Any pearls of wisdom greatfully received!

Engine size, and fuel type, Carbed, CIS, Digi, or Diesel is needed as each has a different style of warm start issues.

Fuel Injection usually doesn't require pedal movement at all on start warm or cold, where as some Carbed Cars require 3 stomps of the pedal prior to start to set the choke.  Had a Dodge, and a GMC that needed this every time…More so when cold than warm.

ie: Digifant uses a CTS sensor in conjunction with a Fuel pressure Regulator.  On start warm or cold, the ignition key should be turned on for 5 seconds at run prior to turning the key switch to Start.

CIS has a fuel pump check valve that can cause the fuel pressure to bleed off when warm. and a WUR that can give greif as well.

Over the years on Carbed cars I have owned,  I have had
fuel run back to the tank sucking the carb bowl dry, automatic chokes fail….Vapor lock on fuel lines that heated up as the engine sat and boiled the fuel as the lines weren't being cooled by running fuel….

Diesels, that had a fuel return and feed  line leak that caused hard starts as more air than fuel was in the Injection pump.

So as I stated more information is needed.

He says it's a gti. 

So it's a 1.6 or 1.8 Petrol injection. 

Roach said

He says it's a gti. 

So it's a 1.6 or 1.8 Petrol injection. 

Guessing and knowing for sure are two different things, as over the years of life, things may have been swapped about a bit.  Years matter as well as year difference between Digi/CIS… and yall do it way different than over here on this side of the pond.

Over on this side, I have seen CIS gutted for Carbs, as well as Digi gutted for Carbs.. Diesel engines installed on gassers and Gas engines installed in Diesels.  

I never assume anything, as I have been proven wrong a time or two on Previously Stock Cars.

could be the fuel accumulator that's in drivers side rear with 2 fuel pipes going to it, some have a flat head screw in the back that if removed fuel should not come out, if it does the diaphragm inside has gone. it holds pressure in the fuel lines so could also check by loosening the fuel supply at the metering head when turned off, if fuel sprays out it is ok

Briano1234 said

Roach said

He says it's a gti. 

So it's a 1.6 or 1.8 Petrol injection. 

Guessing and knowing for sure are two different things, as over the years of life, things may have been swapped about a bit.  Years matter as well as year difference between Digi/CIS… and yall do it way different than over here on this side of the pond.

Over on this side, I have seen CIS gutted for Carbs, as well as Digi gutted for Carbs.. Diesel engines installed on gassers and Gas engines installed in Diesels.  

I never assume anything, as I have been proven wrong a time or two on Previously Stock Cars.

its safe to assume if someone in the uk refers to a gti it is a CIS, also we did not get digifant mk1,s or have air con

Check fuel accumulator as it's job is to hold the fuel pressure in the system to help with hot starts.

Lasts few Gti cabriolets, 91/92 may have digifant injection  system as well as a CAT fitted….
As Briano1234 says, a little more info like year of car, engine code etc is always a good idea, if you edit your signature you can put all the important info so it's always there and you don't have to re type it… See below in my signature.  

well I have never seen a UK spec digifant cabby, or find one now, plenty of 91/92 k jet cars about but no digifants. we didnt have to fit cats in the uk till 1993 so didnt need the digifant to get lower emissions, we had cats fitted to JH engined cars with jetronic ecu on some but its still a cis with added emission control

Thanks for all of the reply's really helpful. Sorry should have mentioned that it's an 83 1.8 GTI. I actually meant to say accumulator as opposed pressure regulator. 

sporttrucker said

well I have never seen a UK spec digifant cabby, or find one now, plenty of 91/92 k jet cars about but no digifants. we didnt have to fit cats in the uk till 1993 so didnt need the digifant to get lower emissions, we had cats fitted to JH engined cars with jetronic ecu on some but its still a cis with added emission control

  You could be right as I'm usually wrong ……. I thought the last few UK cars 92/93 had digifant injection, cat and some even had power steering as VW was throwing on allsorts of stuff to get rid of it?

mark1gls said

sporttrucker said

well I have never seen a UK spec digifant cabby, or find one now, plenty of 91/92 k jet cars about but no digifants. we didnt have to fit cats in the uk till 1993 so didnt need the digifant to get lower emissions, we had cats fitted to JH engined cars with jetronic ecu on some but its still a cis with added emission control

  You could be right as I'm usually wrong ……. I thought the last few UK cars 92/93 had digifant injection, cat and some even had power steering as VW was throwing on allsorts of stuff to get rid of it?

Gee all that stuff was standard equip on the 90ish cabbies over here, and early 90-91.5 we even have digi1 in california as well.

But as I said, given the age of these little guys, and the upgraded interiors and engines/trannys I have seen happen over the years by well meaning previous Owners " Ya just never know what you are working on or looking at."  

Sounds quite interesting, if you have flames coming out of the exhaust there must be unburnt fuel there and the only way it can get there is from the cylinders. It could be the injectors are not sealing.
They do start better from warm on super unleaded aswell, if you're using standard try letting it get low then use that.

Thanks again for all of the knowledge. I don't suppose anybody knows the Bosch part number for the accumulator for the 83 mk1 GTI 1.8 tintop? I've been looking on the Bosch automotive catalog and there seem to be four that match the spec - 0​ 438​ 170​ 027, 0​ 438​ 170​ 028, 0​ 438​ 170​ 040 and 0​ 438​ 170​ 041

Not 100% sure but I don't think it really matters which one you fit as it's just a valve which closes to hold the pressure.
have you removed the screw at the rear to see if petrol pours out?

New accumulator are expensive for what they are.

GSF- use discount code to get it cheaper…
https://www.ebay.co.uk/itm/VW-Golf-155-17-Mk2-1976-1991-Bosch-Fuel-Pressure-Accumulator/302537023712?hash=item46709ca0e0:g:GzIAAOSwh1paEzMa

I think someone on here fitted one of these, slightly smaller but I think it worked?

https://www.ebay.co.uk/itm/0438170015-BOSCH-FUEL-ACCUMULATOR-K-JETRONIC-BRAND-NEW-GENUINE-PART/183034551073?epid=1009506624&hash=item2a9db59b21:g:5EsAAOSww85aaHPl

I think your problem is more likely to be caused by too much fuel rather than too little so probably not a faulty accumulator. You could try cranking it when warm, stopping before it starts then having a look at the plugs to see if they're wet.

cedar said

I think your problem is more likely to be caused by too much fuel rather than too little so probably not a faulty accumulator. You could try cranking it when warm, stopping before it starts then having a look at the plugs to see if they're wet.

The problem of over fueling is the car is being started by pumping the accelerator, (see 1st post) you should not need to touch the accelerator when starting a fuel injection car.  
But yes flames, back firing is to much fuel in the engine.

Wrong type of fuel, timing out, old spark plugs, Ht leads, Dissy cap and rotor could also not be helping starting…..?

mark1gls said

cedar said

I think your problem is more likely to be caused by too much fuel rather than too little so probably not a faulty accumulator. You could try cranking it when warm, stopping before it starts then having a look at the plugs to see if they're wet.

The problem of over fueling is the car is being started by pumping the accelerator, (see 1st post) you should not need to touch the accelerator when starting a fuel injection car.  
But yes flames, back firing is to much fuel in the engine.

Wrong type of fuel, timing out, old spark plugs, Ht leads, Dissy cap and rotor could also not be helping starting…..?

 I did wonder if overfuelling might be an issue, it seemed similar to me to trying to start a carbed engine when warm with the choke wide open. To expand a little, I don't touch the accelerator pedal at all when starting from cold and it starts right up. When the car is warm, if I try to start it withought touching the throttle at best it'll just about start and stutter for a while then go but usually if the accelerator pedal isn't ridden a little when starting from warm it'll just keep turning until the battery goes flat. Plugs were changed about 800 miles ago, not sure about distributor or HT leads. I haven't tried running it on super unleaded but will give this a go too.

the reason the accumulators are fitted is to help with hot starting. does it hot start ok if you shut off then try to restart straight away

there were some digifant mk1 cabs, very late models. very rare to see in the UK, possibly these ones were ordered from dealers in germany. often by either by guys in the forces or people taking advantage of the cheaper price you could, get ordering a UK spec car in germany

anyway moving on, its an 83 GTI. warm start issue could be down to loss of residual pressure. the usual cause is non-return valve in the fuel pump, which is handy becasue its reasonably cheap and easy to change. the accumulator could be leaking inside, if you can undo the small slot drive screw in the end and fuel comes out, you need to replace it, and these can be pricey!

Quick update on the warm start issue. Thanks to all for the great advice above. The issue now seems to be resolved and I didn't replace anything. What I now do differently is run the car on super unleaded and also let the fuel pump run for a few seconds before engaging the starter. The car now starts and runs better than ever. Huge thanks to all who chipped in!