Won't start when engine warm

[keytouch]

1Y 1.9 Diesel engine

Starts fine from cold. When warmed up, if I turn it off, it won't start again. It tries but it sounds like the starter motor isn't getting enough power. Though testing battery shows a good 12.85 volts (brand new battery).

The cables go from battery to alternator to starter (the same way it was wired in the donor Golf). Which starts it from cold.
When warm and not starting, the wire from alternator to starter (which is thinner than battery to alternator) does get very warm.
Could this wire overheating prevent enough power from getting to the starter? Does a hot wire increase electrical resistance?

[colinthefox]

Lots of 1.9s won't start easily when warm.

Your slow starter may well be caused by the thinner wire from alternator to starter. There should be a thick wire direct from battery to starter, and the alternator wire can go to either the battery or the starter. But if your engine starts OK when cold, it should start easily when warm too.

Apart from the slow starter, it may be that your engine needs a short blast of glowplug even when warm. Mine certainly does. You can achieve this by putting a 600ohm resistor in series with the glowplug relay temperature sensor. Thats the one at the rear (forward end of the van) of the cylinder head. If you search this forum for "600 ohm resistor" you should find other threads about this.

In my case overuse of the starter when warm (before I discovered the added resistor) had fried the joints on the interconnection between the starter solenoid and the starter body, so I had to strip it down and remake the joints. But any of the other cables and joints on the starter circuit could be causing your slow starter. You could try turning the starter with the engine cover off in a dark place (care please!). If there's a bad joint you will probaly see it light up when you turn the starter, or at least it will get hot to the touch.

Thin cables have higher resistance than thick ones, and hot cables have more resistance than cold ones.

To remake a bad joint, take it apart, clean it down to bare metal, then reassemble with a smear of copper grease.

[keytouch]

Thank you for such a comprehensive response.
I will give it all a go and see how things work out. And report back.

[simoncummins]

Ive had the same problem with a 1.6 jx engine for a few years i put a new starter on last weekend turn engine over much much faster problem has gone away. The starter that i took off was always the same from when i fitted it years ago i should have taken it back but i would not believe a new starter was at fault.

[keytouch]

Cant see a 600 ohm resistor, would one of these do instead?

560 ohm - http://www.maplin.co.uk/p/metal-film-06 ... stor-m560r" onclick="window.open(this.href);return false;

620 ohm - http://www.maplin.co.uk/p/metal-film-06 ... stor-m620r" onclick="window.open(this.href);return false;

[Oldiebut goodie]

Can send you a couple of 610 ohm (Test at 605/607 ohm) 1/4w if you don't want to use 620s. Maplins are useless for some things. The 620 will just change the delay slightly and would do the job though. pm me your address if you want a couple.

[colinthefox]

Actual value in Ohms is not important. Anywhere 500 through 700. 700 gives more glow, 500 gives less.

Sturdy installation is important, as resistors aren't physically strong. Solder a wire to each end of the resistor leading back along the resistor body. Then wrap the whole lot in shrink sleeve or tape and put a male spade connector on one end and a female on the other. Tape the whole thing to the wiring harness, then it will be immume from vibration.

Note to self.......must put up a photo of this.

[keytouch]

Actual value in Ohms is not important. Anywhere 500 through 700. 700 gives more glow, 500 gives less.

Sturdy installation is important, as resistors aren't physically strong. Solder a wire to each end of the resistor leading back along the resistor body. Then wrap the whole lot in shrink sleeve or tape and put a male spade connector on one end and a female on the other. Tape the whole thing to the wiring harness, then it will be immume from vibration.

Note to self.......must put up a photo of this.

Does the resistor go attached to the engine end or the other end of the wire in the dash?

[colinthefox]

It goes at the engine end.

There are two temperature sensors, one is for the temperature gauge which is in the water flange for the bypass hose at the side of the engine. The wire from this does indeed go to the dash. This is NOT the one you want.

The other temperaure sender is at the rear of the cylinder head in the water flange for the heater hose. (Should be the blue/white wire I think). This is the sensor for the glowplugs, and the wire goes to the black box in the engine compartment. The resistor goes between the sensor and the blue/white wire.

[Oldiebut goodie]

Ideally it should go under the relay in the black box to protect it from vibration etc but it is such a PITA to fiddle about in there that the sensor end is easiest.

[colinthefox]

Tape the whole thing to the wiring harness, then it will be immume from vibration.

[Oldiebut goodie]

Ideally it should go under the relay in the black box to protect it from vibration etc but it is such a PITA to fiddle about in there that the sensor end is easiest.