VR6 hot start problem seem to have been resolved - just thought I'd post experience

[Mawrick 0]

Ever since I got my 96 VR6 it have had a hot start problem - not always but most of the times, especially if one stop for fuling, or just to pick up some stuff from a shop, and then continue on the drive (restart within 10-25 minutes), never any errors with vag-com, changed different things including cam position sensor to no avail.

 

Eventually I ended up buying a non return valve from ebay I hooked up to the fuel feed line (under the tank cover), and now this problem seem to be gone.

 

(I have yet a bit more testing to do, but before I daily experienced long "crank" time when it was hot), but after the non return valve was put into place this problem seem to be gone - just thought I'd post this for other experiencing weired hot start problems :)

 

(VW used to have a fix for this but sadly discontinued)

[seanl82 23]

Or just replace the fuel pressure regulator for a proper solution? All the non return valve will be doing is holding the fuel in the rail anyway mate.

[Mawrick 0]

Or just replace the fuel pressure regulator for a proper solution? All the non return valve will be doing is holding the fuel in the rail anyway mate.

 

Don't think that would resolve it - IIRC I tried 2 different FPR's (and/or did that test to check the FPR) - but AFAIK this was a known problem from VW - and I guess they wouldn't have made the "check valve" fix they did (discontinued) if the FPR was to blame......

 

The "fix" they had for leaking fuel pumps:

 

[Roger Blassberg 0]

Can you be more specific about the non-return valve you bought from ebay please? Was there an item number for the valve?

 

Thanks

 

RB

[robrado974 1]

Thanks for posting the solution I have similar problems but only now and again , I've tried another pump as well mine goes in Thursday for a pressure check as I'm out of ideas now !

[VW_OwneR_85 1]

I don't get how this problem would only happen on hot starts, surely it would happen from every start, more so first thing in the morning/when the cars been idle for long enough for the pressure in the line to back into the tank..

[robrado974 1]

Corrado's can be very strange . Cold start yes I could see the problem because the fuel has gone back down the pipe , but once started it should be fine for around 15 minuets after turning off the ignition to restart the car , then after said time it will be harder to start . This is what I'm getting ATM on and off .

Rob

[Mawrick 0]

I bought this one myself:

 

http://www.ebay.co.uk/itm/271061850109?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

 

I'v got no idea why this only happen for hot starts, but something is it, I'v had this problem from when I got the car (years ago), but only recently started to do real troubleshooting into the problem, and got info about this fix that VW had issued with the hose and non-return valve (due to hot start problems on the VR6) on a german forum. This hose thingy isn't available anymore from VW but you could do the same with this non-return valve.

 

The way I did it on mine:

 

bought some extra 8mm fuel hose, connected the new hose directly to the pump, routed it around the top of pump (where the hatch for fuel pump is), cut it to lengt, connected the non-return valve (correct way :) ), and then connected the valve up to the original hose (without cutting it).

 

I haven't had one single problem with hot starting after I did this, and before I had them daily......

[poll250 0]

[ATTACH=CONFIG]75569[/ATTACH]

 

I bought one of these to fix my hot start problem a while ago, still haven't gotten round to fitting it though!

[jonnykillpop 10]

Had similar prob hot starting and was just the fuel pump relay, take the cover off the fuse box after run feel the fuel pump relay if it's pretty hot to the touch needs changing, mine was feeling very hot just touching cover so imagine what the workings are like inside, give it 15 mins to cool and started fine. Swapped mine for relay in wifes little Seat(same one 167 from memory and started straight away) then got new one plus ecu relay which was getting bit too warm too, and perfect starting since. Cheap easy fix so worth looking at first.

(Had exactly same prob on few high tuned V6 Capri's, big hot V6's, relays sit exactly same place in drivers footwell, and manifolds run close drivers side bulkhead, their gonna oveheat and give up eventually)

[fendervg 32]

Still intrigued by this solution. The FPR regulates the pressure in the rail, but the non-return valve described here will stop fuel returning back to the tank down the return hose from the rail, thus keeping more pressure in the system. This should help with cold starts, as the pressure will usually drop over time. However, I would have thought that the pump priming will give enough pressure for a successful start, although maybe a bit longer crank time than you would get with a hot engine and higher pressure. The only way I could see it helping maintain pressure to a hot engine is if there is already another problem such as leaking injectors or hoses present. This could manifest itself only when warm due to heat expansion. Provided the system is functioning as designed there should always be enough residual fuel pressure there.

 

Does anyone have the original German thread reference that mentions the VW fix? I'd like to do some more investigation on this. I've also read of a breather valve on the pump assembly or near the filler cap, but have yet to track it down.

 

EDIT: just looked at an old fuel rail I have here, and the FPR is a variable flow non-return valve that will regulate the amount of petrol going back down the return feed from the rail, so there should be no need for another one. Hmm. However, if your injector seals were shot...

Edited August 28, 2015 by fendervg

[Dox 23]

Still intrigued by this solution. The FPR regulates the pressure in the rail, but the non-return valve described here will stop fuel returning back to the tank down the return hose from the rail, thus keeping more pressure in the system. This should help with cold starts, as the pressure will usually drop over time. However, I would have thought that the pump priming will give enough pressure for a successful start, although maybe a bit longer crank time than you would get with a hot engine and higher pressure. The only way I could see it helping maintain pressure to a hot engine is if there is already another problem such as leaking injectors or hoses present. This could manifest itself only when warm due to heat expansion. Provided the system is functioning as designed there should always be enough residual fuel pressure there.

 

Does anyone have the original German thread reference that mentions the VW fix? I'd like to do some more investigation on this. I've also read of a breather valve on the pump assembly or near the filler cap, but have yet to track it down.

 

EDIT: just looked at an old fuel rail I have here, and the FPR is a variable flow non-return valve that will regulate the amount of petrol going back down the return feed from the rail, so there should be no need for another one. Hmm. However, if your injector seals were shot...

 

The non return is placed between the pump and FPR to maintain pressure when the pump is stopped, the return to the tank remains untouched as I read it?

[fendervg 32]

Ok - that makes sense - maybe there was trouble with fuel seeping back down through the feed line and into the pump. But it would have to get through the one-way fuel filter (there are directional arrows on it when fitting) and the valve in the pump on it's way back! The VR is not a high pressure system like the mechanical injection on the K-Jet 16v cars, so should not need a high residual pressure. So I read it that the closer the non-return valve is to the fuel rail along the feed line, the better the result. Or am I wrong?

[Dox 23]

Ok - that makes sense - maybe there was trouble with fuel seeping back down through the feed line and into the pump. But it would have to get through the one-way fuel filter (there are directional arrows on it when fitting) and the valve in the pump on it's way back! The VR is not a high pressure system like the mechanical injection on the K-Jet 16v cars, so should not need a high residual pressure. So I read it that the closer the non-return valve is to the fuel rail along the feed line, the better the result. Or am I wrong?

 

I've not changed a VR filter (its on my to do list), but other filters I have changed would pour out of either end suggesting there is no one way valve inside the filter itself? I use lots of filters at work with direction indicators on, there is reinforcement in one direction only to prevent the filter element (card / paper) being dislodged and causing havoc down stream, I presume the fuel filters are the same? If the filter collapsed you wouldn't want bits of filter element stuck in an injector for example.

 

Providing the pressure is at the injectors I can't see why you couldn't fit the non return in the engine bay should you wish to do so?

[fendervg 32]

I suppose for given the price of a fuel filter there would probably not be a valve in it. I do know though that the many of the VAG oil filters have a non-return valve in them, and that some of the lesser quality replacements don't. That leaves the fuel pump valve then as the suspect, provided all else is ok.

[Jim Bowen 1]

I have a feeling the corrado fuel filters have some of valve in it. Am sure i remember fuel would only spill out of one end when changing it. They deffo have and arrow on. My car also has that little silver valve shown on previous page.

 

Also seen the breather valve on tank neck.

 

Just replaced all the rubber fuel lines for ptfe stuff. I wonder if a slight split in a hose might cause air to get sucked in when car isn't running. I had a fuel leak once but wouldn't leak everytime i started car. But other times it would cone out at quite a rate. Them rubber hoses are all 20yrs old now even in the youngest corrado.

[Jim Bowen 1]

Bloody phone missing or mistyping words. Am sure smart phones cause more typing errors than we used to have.

[Dox 23]

I suppose for given the price of a fuel filter there would probably not be a valve in it. I do know though that the many of the VAG oil filters have a non-return valve in them, and that some of the lesser quality replacements don't. That leaves the fuel pump valve then as the suspect, provided all else is ok.

 

If cheap oil filters that don't have the non return fitted are used oil drains back to the sump when the engine is stopped allowing the tappets to also drain and make a row on start up, the non return on a VR6 is fitted to the block? as the filter is just a paper element.

[Dox 23]

I have a feeling the corrado fuel filters have some of valve in it. Am sure i remember fuel would only spill out of one end when changing it. They deffo have and arrow on. My car also has that little silver valve shown on previous page.

 

QUOTE]

 

I've just been into the garage and blown through either end of a new filter with my mouth, no one way valve fitted to this one.

[fendervg 32]

At least that's that part of the mystery solved! My car is a 93 and has no valve fitted. Do you have any photos of it in place and is there a part# on it? Maybe they were only ever fitted if a car came back to the dealer with starting problems.

[Dox 23]

I will say my car is starting much better with the preloved pump fitted, even though its quite noisy in operation. When I removed the pipes to the previous pump only a small amount of fuel leaked out under hardly any pressure

[fendervg 32]

I'll do my fuel pump saga write up this weekend hopefully and post it in the Supplier's Forum. I'm going to buy one of those valves just to see - will be interesting to observe what happens to the residual pressure with one fitted nd how quickly the engine starts hot or cold.

 

@dox - sounds like your old pump was really knackered. Was the one you put it in an identical model from a same era car? Would be interesting to know if it was a Pierburg unit or had a VDO pump inside. Sadly they only open with Torx screwdrivers and I didn't have any around when I had mine out.

[Dox 23]

I'll do my fuel pump saga write up this weekend hopefully and post it in the Supplier's Forum. I'm going to buy one of those valves just to see - will be interesting to observe what happens to the residual pressure with one fitted nd how quickly the engine starts hot or cold.

 

@dox - sounds like your old pump was really knackered. Was the one you put it in an identical model from a same era car? Would be interesting to know if it was a Pierburg unit or had a VDO pump inside. Sadly they only open with Torx screwdrivers and I didn't have any around when I had mine out.

 

My pump itself was fine, the centre part of the swirlpots rubber mounts had fallen apart and rotted away, the replacement out of my storm was different with the rubber hangers on the outside of the pump, the original pump had a steel ring sandwiched between upper and lower parts with the rubber hangers inside the pot itself.

[fendervg 32]

Ok. I remember that from the other thread. Did you swap over the whole fuel delivery unit or just the pump, and did you have to change over the sender?

[Dox 23]

Ok. I remember that from the other thread. Did you swap over the whole fuel delivery unit or just the pump, and did you have to change over the sender?

 

Chucked the whole lot in, the pump seems to be a press fit into the centre part of the swirlpot