Engine not starting... what to check?

[eddie124]

Hi all,

I finally got the engine loom worked out and put together on my '88 Tourer's pre-facelift 2,5 engine (out of an '86 325is). Using all the kit that Mark (town325i) kindly supplied me with, I replaced the whole loom, oil sensors, crank trigger, ecu, etc.

Everything is now in place, but even though the starter turns the engine over just fine, it won't start. Here's what I've checked so far:

- C101 terminals oxidised (were looking ok, but cleaned them anyway)
- Fuel pump stuck (tapped it, worked fine on its own)
- Fuel pressure (has pressure and maintains it)
- Spark (has got it)
- Spark plugs (they're new or look like it)
- intake boot (got a few cracks and splits but I tucked it onto a position where it looks straight)
- alternator wired in (no belt but it's wired up correctly)
- HT leads in their correct position
- Immobiliser plug (ok and correctly bridged terminals)

Things I still doubt:

- Battery not powerful enough (it's a 50 Ah unit, fully charged so it cranks over fine)
- Starter connections (the famous black/green wire is permanently grounded, not wired through the starter)
- Alternator: does it need to be turning for the engine to fire?
- Injectors: I used the original ones, as though this is a pre-facelift engine, it is a 2,5 so it's also a Motronic-managed unit
- Vacuum leaks: are small splits on the boot enough for the engine to not start? They're tucked together, but I suppose I could get them sealed.

When I turn the ignition to run position, the startup valve makes a light buzzing noise, as does the ecu. Is this normal?

I've tried feeding the pump directly or running it normally, makes no difference.

Any other thoughts of things to check, please contribute them.

Cheers, Eddie

[town325i]

Have You put the crank sensor wire and the number 6 plug wire the right way round try them the other way round just to make sure.

These are the plugs under the diagnostic port on the inlet manifold

[eddie124]

Hi again Mark,

I double checked these, as they were something that could easily be swapped. You tagged them and I got them wired up correctly according to the labels.

I did just try them the other way round, but still the same... cranks over, but no joy.

[eddie124]

I read somewhere that the ground line that plugs into the starter is meant to de-energise as the starter is cranked (gets battery voltage so no potential drop across it), can this be the problem? I wired mine directly to the engine for a permanent ground.

There is a terminal on the starter that I've not used (and doesn't appear to have been used before), opposite the terminal for the ignition line. I tested it, but since it didn't read any passage to ground with my multitester I ignored it and wired the line directly to the block.

[Brianmoooore]

I read somewhere that the ground line that plugs into the starter is meant to de-energise as the starter is cranked (gets battery voltage so no potential drop across it), can this be the problem? I wired mine directly to the engine for a permanent ground.

There is a terminal on the starter that I've not used (and doesn't appear to have been used before), opposite the terminal for the ignition line. I tested it, but since it didn't read any passage to ground with my multitester I ignored it and wired the line directly to the block.

You've lost me here! There's no ground or ignition connections to the starter motor. The only connections are a permanent live, the start signal, and the black/green wire from the unloader relays that you've mentioned earlier.
Am I right in thinking this is a pre facelift engine converted to post facelift (1.3) management?
Are the tips of the spark plugs wet after a cranking session?

[eddie124]

Hi Brian,

Sorry for not making it clear. Yes, I meant the black/green wire that we talked about earlier. I read somewhere that during cranking over this terminal gets 12v+ so the unloader relays switch off while the starter is working. Mine is grounded directly to the engine, though.

Yes, this is a pre-facelift engine that's been converted to 1.3 Motronic. I can't be sure about the plugs being wet, but when I got #1 out it did look a bit moist. I'll give it another go and see immediately afterwards to make sure.

[eddie124]

Well just tried it again. Thing is, because the plugs are new there's no deposits on them to actually make them look wet, but it did smell of petrol. Any ideas?

[Brianmoooore]

They should be dripping wet after a cranking session if it doesn't start.
Any access to propane? In cases like this I pull the fuel pump relay, depressurise the fuel system, remove the rubber boot from the throttle body, take a bottle of propane with a hose and tap attached (actually a gas blowlamp with the jet and nozzle removed) and crank it while feeding gas into the TB.
Propane will fire up over a wide range of mixture strengths, and will not foul plugs, unlike that unsuitable, expensive petrol stuff that most of you run your cars on for some reason, so if it fires up you know that sparks, timing and compression are all OK, and the problem is with the fuel system.

[town325i]

They should be dripping wet after a cranking session if it doesn't start.
Any access to propane? In cases like this I pull the fuel pump relay, depressurise the fuel system, remove the rubber boot from the throttle body, take a bottle of propane with a hose and tap attached (actually a gas blowlamp with the jet and nozzle removed) and crank it while feeding gas into the TB.
Propane will fire up over a wide range of mixture strengths, and will not foul plugs, unlike that unsuitable, expensive petrol stuff that most of you run your cars on for some reason, so if it fires up you know that sparks, timing and compression are all OK, and the problem is with the fuel system.

Or you could pull fuse 11 take plug out and refit it to the plug lead and hold it on the rocker cover somewhere to see if you get a spark.

Brians method does sound like a good one though

[eddie124]

I didn't crank it for long, mind. But since the plugs are brand new (the kid who sold it to me had been scratching his head trying to make it run with the pre-facelift wiring in place, so he got new plugs), it's hard to see petrol on clean metal.

Only small gas canisters I've got here are a small camping burner and a handheld torch.

BTW, where is the fuel pump relay?

I'll give it another go later on with the Spider's battery (bigger 70 Ah unit) to trace the wet plug sindrome, but I'll keep your suggestion in mind.

I think the Fiat's plugs are the same size, I'm going to compare them. If so, I'll get one of the cylinders fitted with a used one for a better look at its wetness after cranking for a while.

Returning to the black/green wire, is it ok to leave it grounded permanently?

[Brianmoooore]

They should be dripping wet after a cranking session if it doesn't start.
Any access to propane? In cases like this I pull the fuel pump relay, depressurise the fuel system, remove the rubber boot from the throttle body, take a bottle of propane with a hose and tap attached (actually a gas blowlamp with the jet and nozzle removed) and crank it while feeding gas into the TB.
Propane will fire up over a wide range of mixture strengths, and will not foul plugs, unlike that unsuitable, expensive petrol stuff that most of you run your cars on for some reason, so if it fires up you know that sparks, timing and compression are all OK, and the problem is with the fuel system.

Or you could pull fuse 11 take plug out and refit it to the plug lead and hold it on the rocker cover somewhere to see if you get a spark.

Brians method does sound like a good one though

Claims to have spark in the OP.

[Brianmoooore]

Fuel pump relay is under the cover by the air filter. Four pin one, with a green/purple wire going to it, amongst others.
Leaving the black/green grounded permanently isn't good practice, but it won't have much relevance to your current problems. It should connect to a terminal with a 8mm nut on the starter solenoid, or it can be connected to the inner 13mm nut - the one that has a braid or strap going to the starter motor itself.

[eddie124]

Hi again guys,

Yes, I do have spark. I'd tested the coil and it was getting current, but just to make sure I got a mate to crank it while I checked a plug. Nice fat spark.

I also checked the cam timing and it appears ok. The engine turns over easily so nothing's sticking either. Builds up oil pressure very quickly when cranking too, the light goes out after less than a second.

My starter solenoid does not appear to have the 8mm nut. Even the starter signal line had a ring terminal but on my starter it's a spade connector so I had to change it. I did use the ring terminal on the black/green wire to bolt it onto a bracket on the engine for a ground.

There is an extra spade terminal (male) on the solenoid which is what I'd mentioned above, can this be the connection for this wire? It doesn't appear to have been used before judging by the corrosion on it.

I will get it connected properly as soon as I can, I don't like things done the wrong way.

Brian, if the plugs are getting soaked, what can be the issue? AFM or TB giving wrong signals? Fuel pressure regulator not working properly? Injectors?

I was wondering about the relevance of the cracks on the intake boot, but I get the feeling that these shouldn't be an issue with startup, just with running at speed, am I right?

I have been told this engine was running (in the 325 is sedan it originated from) not long before it was put into the tourer, but even that may have been over 6 months ago so it's been sitting around doing nothing. Or rather, the kid did try to get it started but he was using the pre-facelift loom so things were not wired properly and he gave up. That's when I got it...

[Brianmoooore]

If the plugs were very wet and it has a "big fat spark", I would be struggling, as it should be running! These engines aren't complicated - spark at something like the correct time, reasonable compression, and a air/fuel mixture in the ballpark of the correct ratio and it goes in some fashion or other. The only sensor of great importance is the crank one, and without this it doesn't spark.
Engine should start and idle fine with the big rubber air tube off of the engine.
The small gas bottles should be OK, as long as you can remove the jet. Gas tap won't need to be turned on very far.

[eddie124]

Brian, for me the problem is the plugs are brand spanking new, so I can't judge their wetness at all. They just smell of petrol, but I can't see it. I'm going to check their size compared to the Fiat ones I use on the twin-cam to see if one of those will fit, and try that if it does to see how wet it gets. If it turns out not to be getting petrol, I'll give the gas a go.

There is a strong spark, yes, I could see it easily even in bright afternoon sunshine so I don't think this is the issue.

I got all the old petrol off as far as I could get it pumped before I got the new petrol in the tank too, and the fuel I'm getting at the pressure regulator doesn't smell like old petrol either.

I'm now surveiling an exam but I'll be home by lunch so as soon as I have a spare moment I'll get under the bonnet again... I'm dying to hear that six running!

[eddie124]

Ok so the update (man, the Zone is big, give it a few days and you walk through 4 pages finding where your topic's been blown to!):

The spark plug is clean, no wetness at all. Confirmed this twice with a used plug. Engine turns over fine, cam timing is spot-on.

When I gave it a couple of tries now with a bigger battery (from the Spider), the starter ran noticeably faster so that wasn't helping either.

Anyway, after that I spotted a fuel leakage from the fuel filter where a hose clamp was loose. Tightened it up, and tried again. Pump is doing its job, fuel pressure is up, and reaching the regulator. I pulled out the hose and got everything sprayed with petrol. Just to make sure it was pumping, I got it running onto a can over a few turns and it pumped fine.

So, what's next on the checklist? I'm going to try the "gas down the TB" suggestion later today, but wanted to get you folks up to speed on this.

[town325i]

Are the plug leads in the right order on the cap? they are marked on the cap what lead goes to what cylinder

[eddie124]

Yep, double checked this twice.

BTW, I've just found three wires right by the TPS connector that were cut. I was just replacing the tape that was loose but when I got it out I found right besides the TPS wires an extra set of 3: one yellow, one brown, one black. Any idea what these are?

[town325i]

They are for an auto tps and thats what i did to use a manual tps not knowing at the time i could of used an auto tps i did it 3 years ago

[Brianmoooore]

Ok so the update (man, the Zone is big, give it a few days and you walk through 4 pages finding where your topic's been blown to!):

The spark plug is clean, no wetness at all. Confirmed this twice with a used plug. Engine turns over fine, cam timing is spot-on.

When I gave it a couple of tries now with a bigger battery (from the Spider), the starter ran noticeably faster so that wasn't helping either.

Anyway, after that I spotted a fuel leakage from the fuel filter where a hose clamp was loose. Tightened it up, and tried again. Pump is doing its job, fuel pressure is up, and reaching the regulator. I pulled out the hose and got everything sprayed with petrol. Just to make sure it was pumping, I got it running onto a can over a few turns and it pumped fine.

So, what's next on the checklist? I'm going to try the "gas down the TB" suggestion later today, but wanted to get you folks up to speed on this.

I think I see a clue in the above!
Are the fuel pipes on the correct way around?
Fuel pressure should NOT be reaching the regulator by a hose.

[eddie124]

You mean the regulator is meant to be on the output side of the fuel rail? Makes sense to me. I only connected them by the logical placement they had, but maybe whoever fitted the engine swapped them not knowing which way round they went.

Will try to swap them round in a few minutes.

[eddie124]

Brian, you were spot-on.... IT LIVES! Just spluttered right into life after a few churns!

I can't begin to tell you how chuffed I am... it wasn't my mistake, they were already put on that way and I only followed suit.

Mark, Brian, thanks a million to both of you for guiding me through the rough bits, you've just made this first-time E30 owner one very happy boy!

Now I'm really looking forward to a summer of slowly sorting the rest out!

Cheers, Eddie

[124spider]

Parabéns Eddie!!

[town325i]

Good work Eddie hope you enjoy your first E30