BKD wont start

[skibbler]

I've bought a 2008 caddy that was originally an sdi but now has a bkd fitted. It doesn't start off the key but runs fine when u bump it off. I was told by the previous owner that it used to start off the key, gradually took longer to start untill one day it wouldn't. Its tuned to over 300hp with darkside parts so I have to believe him, who would spend all that money if it didn't start.

So far I've changed...
The starter cos it was seized
The battery cos that was toast
Ive checked the earths
Checked that I'm getting fuel
Scanned to find lots of codes that looked like they were linked to things being unplugged. I currently have glow plug control module implausible signal.

Would glow plugs prevent the car from starting? Im a bmw man and they always start with glow plug problems. Im reading mixed things about the location of the glow plug control and relays. I don't have the unit under the fuse box or the wiring for it. I have the 101 relay in the fuse box that I've tested and works. I have the wiring and holder for a relay or controller behind the passenger side light but nothing plugged in.

I'm also leaning towards the asv/imf maybe being stuck. However would the engine then run when bumped off? The pressure opens it maybe?

People have suggested the tandem pump and also the crank sensor which im going to check tomorrow.

Any help with be greatly appreciated.

[SRAutoSolutions]

start with the basics before throwing money at it.

Do you have diagnostic equipment capable of live data?

Do you have a crank signal? (symptoms fit)

[skibbler]

So far I've narrowed it down to possible Crank sensor or wiring fault. There was a code for g28 intermitant signal.

I've changed the starter and battery which were both toast. I'm assuming from the previous owner trying repeatedly to start it.
I've checked for fuel at the filter.
When cranking there's a delay before the rpm gauge moves and it sits under 200rpm.
Im going to check the Crank sensor wiring and also the ecu for water ingress then next step change the crank sensor.

[Doc]

If the ECU is only registering 200RPM, it won't permit start of injection.
Have you tried just unplugging the crank sensor to have the ECU run off the cam sensor reference only?

[Exuptoy]

I bought my 56 BLS with long start issues. PO had replaced crank sensor and injector wiring.
Van would eventually start then go into limp mode and when scanned show cam sensor and EGR fault. After googling fault codes I found a few videos on the Tube showing long start issues caused by wiring faults.

Turns out the plastic corrugated conduit which starts under the air box and runs up the front of the engine causes multiple indentations in the wiring caused by the corrugations rubbing through at the bend at the lower end of the loom beneath the airbox. I removed the conduit, pulled each wire which promptly broke in two. A new piece soldered into 4 wires and heat shrunk then the loom re taped allowed me to drive the van home with issue. All faults cleared and none returned.

You can confirm this by checking the cam sensor plug. With a multimeter and the ignition switched on, you should find earth continuity from one wire to earth, perm 5v on another and 5v reference on the final one. I had lost my 5v reference.

[skibbler]

I haven't tried unplugging the Crank sensor yet. That is next along with checking the wiring. The plug for the Crank sensor seems very hard to access.

I get very little time to work on it so it's 15 mins here and there. I have to quickly try something each time.

I'm fairly sure at this stage I have a wiring fault.

So Doc if I unplug the Crank sensor the ecu should then start off the camshaft sensor signal?

[Exuptoy]

Not if you’ve a wiring break to the cam sensor as I posted above.

Easy check if you have half hour spare. Remove clamps off airbox intake, and I think 1 bolt near the battery to remove the airbox then remove corrugated conduit cable trunking. If wires have evidence of serration in the cable insulation near the lower bend where it comes off the chassis rail beneath the airbox, give them a tug to see if they snap. Odds on they will.
Easy fix if you are competent with a soldering iron and some heat shrink.

[skibbler]

Had a day off today so i checked the wiring from the ecu to the crank sensor. All appears fine.

I think before i commit to pulling everything off to change the sensor ill invest in vcds so i can check live readings when cranking.

Seem to have narrowed it down to the sensor now tho.

[skibbler]

Ok so bit of an update.

Changed the crankshaft sensor and checked all the wiring which initially didnt change anything.

Bumped it off today and drove round the block. After turning it off it fired up straight away. I turned it off and waited a few minutes, it chewed for a few seconds and started. Turned it off and left for 10 mins and it wouldnt restart.

So now i guess were looking at a leak in the fuel system or faulty pump?

[NZDubNurd]

This can also be a starter motor issue. As they get older, they crank slower. When the engine is hotter, they are less likely to start.

Clearly your crank signal wasn't 100%, so at least that's sorted.

As doc said above, you have to reach the minimum crank speed for it to fire and starters have been a fairly common cause for that.

You can watch the crank speed in VCDS too.

[skibbler]

I think we can rule out the starter, that was the first thing I changed
It will not start after being sat. Once running if u turn it off and try to start it straight away then it'll start. The longer u wait the harder it is to start untill after maybe 5-10 mins it won't start at all.

[NZDubNurd]

For a NEW/rebuilt starter, or a used one? A local guy fitted 3 used ones, before a new one worked for him

You can easily rule it out by watching the cranking speed in VCDS. I thought the minimum was 250, and should be about 280 rpm?

[SRAutoSolutions]

Any further on with this?

The way you describe having to start it could also be a leak in the fuel system allowing it to run back as soon as the engine has stopped, quite often leak off pipes (if your van has an engine that uses them), could also be an injector problem.

When was the last fuel filter change?

[skibbler]

Ok glad u said this.

I think I have norrowed it down to a fuel pressure issue and potentially Injector seals. The van will start up no problem at all straight after its bene running. The starter is fine and all sensors.

I have changed the tandem pump, in tank lift pump and also the fuel filter and housing already.

I bumped the van off and clamped the return line. It helps for say an hour. U can start it within 15 mins no problem. Say 15-30 mins and it chews before starting. If u leave it an hour uve got no chance.

Would u agree this leans towards injector seals? I have a positive deviation on cylinder 3 but its only 0.75. Don't know whether to assume its cylinder 3 or just do all 4.

[theoldseacaptain]

Sounds similar to some issues you get if the flow and return have been swapped round - maybe during the conversion? Worth a check both sides of the filter if you haven't already....