ALH no start, I'm stumped!

Hi guys,

My mechanic recently rebuilt an ALH, but the engine wouldn't start. It cranks, but there is no firing whatsoever, no stumbling, no rough idle, nothing. Not even a pop. Compression is fine, everything before the ASV is disconnected so its not a choked intake. There is suction at the ASV as we crank, so air is definitely going in. ASV remains open throughout. Fuel-wise we have changed 3 known working pumps and 2 known working sets of injectors, no joy. Fuel does squirt out when we loosen the injector heads to bleed the fuel, albeit with less pressure than I remember mine having. Or maybe it's just me. Relay 109 changed as well, glow plug light comes on for a brief moment when we turn the key. We even tried a direct fuel line from the pump to a container of diesel. Vagcom doesn't give any codes, nothing looks abnormal. The only thing strnge is that vagcom does not give me a fault code when I unplug the maf.

Any ideas anyone?

Cam timing and pump timing has also been checked and rechecked, he has bulit a lot of ALHs in the past, so I'm pretty confident he is spot on

It is sorta possible to time engine with cam 180deg out. Slot at cam end is parallel to head, but flipped. Make sure #1 cyl cam lobes are not pressing followers (lobes up), #1 being at timing belt end of engine.

Also, if no white smoke comes out tailpipe when cranking, no fuel is being injected.

I think we can assume that your mechanic knows how to bleed the air from the injection pump.

I am thinking that there is an electrical problem. Did it run before the rebuild?

Fuel should be forcefully expelled from the cracked line nuts at the injectors during cranking. If it's dribbling out then either the pump is not "on" (check the shutoff solenoid) or it is not pumping (airlocked, etc.)

If there is no white smoke coming from the tailpipe then no (or close to no) fuel is going in. If you're getting fuel but it is not igniting it has to go somewhere, and the "somewhere" is out the back end as white smoke (unburned fuel.)

Thanks for the suggestion guys, we checked the timing again last night, that was spot on. But a strange thing, we swapped the injectors last night, and this time, we couldn't get the pump to prime anymore. All there was at the injector nuts was a dribble of fuel. So we thought, YAY, we're probably just unlucky that all 3 pumps were spoilt. This morning we swapped in yet ANOTHER pump but still no joy! There was no fuel coming in from the cracked nuts. Now I'm really stumped. We tried running the fuel intake line directly into a container of diesel, no go either. We also tried giving the fuel shutoff solenoid a direct 12V to force it to stay open, no go either. No white smoke or anything like that. We'll be working on it again later, keep you guys posted!

VCDS show engine rpm when cranking? Could be a problem with crank position sensor.

Well, you could put a couple more pumps on it, or you could troubleshoot why the computer isn't turning the fuel on. It requires more than just 12 volts to the shut-off solenoid. The computer controls when and how much fuel is injected so if the injection pump isn't getting any signal, it won't inject fuel.

you are experiencing a loss of prime at the injection pump and fuel lines.

in extreme cases like this, when you prime the pump, supply fuel directly to the fuel inlet of the injection pump with a funnel.

disconnect the fuel supply to the injection pump inlet, connect a funnel, and keep the funnel full as you draw vacuum on the nipple off the return line fitting on top of the pump. This requires a helper usually

suck fuel through the pump this way until you see no bubbles, then continue to suck another 15 minutes past when you THINK it is primed. to ensure prime

start and run the car keeping fuel in the funnel for at least 30 seconds. this will require a helper.

Then shut off the car, make sure the fuel filter has fuel in it, make sure the fuel line is full.

Car may stumble a few seconds after you run it from the fuel tank again, as the fuel lines re-prime. if you stall and can't start, repeat the process, making sure to clamp off the fuel supply hose to prevent draining back to the tank again

My solution to this problem is a small in-line diesel-rated fuel pump. Connect it on the INLET side of the fuel filter (it has a set of alligator clips for power) and you now have a pressurized fuel feed. If you have an air leak at the filter or pump itself this will also tell you immediately because when the pump is energized it will maintain a modest positive pressure in the system and that will cause the point of the airleak to leak FUEL, making it much easier to find and fix it.

I have a general practice of never supplying fuel to an IP that has not been filtered; when I prime I either pull fuel from the return side (and thus through the filter) or I apply a pressure feed to the inlet of the filter.

vag com should tell you whats not happening , if you have air in the system you should get a low fuel pressure code , im not sure what it should be for a caddy as ive not had any problems with mine.
are you using vag com lite or full ?
lite will only give you live faults

An ALH doesn't monitor fuel pressure.

Thanks for the inputs guys, van still wouldn't start. We have fuel coming off the cracked nuts now, we even pulled the injectors and yes, they are spraying. Still no start though. It baffles me how a diesel can get air, compression and fuel and still not get a single 'pop'. Even if timing was waaaaay off, it would at least stumble for a bit. We are going to take the engine apart tonight, so fingers crossed

P.S. I just learnt from my mech that the guy who worked on the engine was the new mech, who just left the company recently. Now that opens up a lot of possibililties as to what may be wrong. I even doubt he actually ran a proper compression test. We are going to check everything from scratch again. It's annoying to have to go through someone else's work!

vogelspinnen said:

... It's annoying to have to go through someone else's work!

Click to expand...

Even more annoying to have to do it for free because you had a bad employee and the client can't be expected to pay for bad labor!

Before you go tearing things apart, remove cam cover and roll engine to where IP pin hole is lined up (12oclock relative to pump body), flywheel is at tdc mark, and now the important step- make sure #1 cylinder (at timing belt end) has cam lobes NOT pressing on cam followers. Lobe tips should be aiming somewhat UP.

yeah the timing mark on the flywheel could be wrong too

Good point. Might want to pull an injector and get a rough check on TDC by feeling piston top through the inj hole.

Cheers guys, engine is started! Turned out it WAS a stupid mistake made by the ex-employee. Timing for the pump was WAY off, it was basically injecting on the exhaust strokes so everything just went out the exhaust. Can't believe it was such a simple fix, everyone expected the timing to be spot on since the new guy said he 'checked it thrice'. Thanks for all the input, I appreciate it guys.

Oh, and as to why the pump wouldn't prime, he didn't secure the signal wire to the fuel cutoff properly. My guess is that fuel was cut off intermittently as the engine shook when we started it.