m20b25 non start help needed

[steve_k]

Help needed.

Got a non start issue with my m20.

Recently changed the timing belt, water pump & fitted a rebuilt head.

Came to start the car today & it won't start.

Symptoms are.

The battery was pretty low so charged it up before trying to start the engine.

Engine turns over but won't fire up. When it's turning over there a slight/faint cough like its trying to start.

No spark, found out by taking a plug out, placing it on the rocker cover & tried starting the car, tried this on all 6 plugs no spark on any of them.

There's fuel at the FPR/fuel rail (had a split hose so I knew there was fuel there).

So I'm fresh out of ideas & I don't want to start replacing parts just for the sake of it.

So, does anyone have any idea what could be wrong??

edit, have checked the resistance of the CPS & it's reading 0.51ohms, but from what the wiki says it should be 540 ohms (+/- 10%).

could this be the issue??

[steve_k]

anyone??

[BenHar]

Have you worked through this: https://www.e30zone.net/e30wiki/index.p ... oubleshoot

Ben

[steve_k]

Have you worked through this: https://www.e30zone.net/e30wiki/index.p ... oubleshoot

Ben

thanks ben i'll go through that later.

[steve_k]

right i've read through the guide in that link,

the battery is a known good one with a full charge,

so far i know there is fuel getting to the fuel rail,

i know that the starter motor spins freely.

the cambelt is a new one & the motor turns over freely, both on the starter & by hand,

have checked for spark by removing a plug & leaving it in the lead & grounding it on the rocker cover & trying to start the engine, no spark, not even a weak one.

have yet to test the coil,

have checked the resistance of the CPS & it's showing 0.51 ohm's across pins 1 & 2, across pins 1& 3 it shows an "OL" reading.

i'm no exspert but it leads me to think that the CPS is at fault due to the fact the OHM's reading is miles off what it should be.

so, does anyone have any more ideas??

[BenHar]

Sounds as though the CPS is the problem.

Check that it's not just a broken wire in the CPS loom though.

Ben

[steve_k]

Sounds as though the CPS is the problem.

Check that it's not just a broken wire in the CPS loom though.

Ben

I'll remove it & check the full length of it,

Got a new sensor on the way just in case.

[Brianmoooore]

I strongly suspect your reading of 0.51 ohms is actually 0.51 kilo ohms = 510 ohms. If it really is 0.51 ohms, then the lead to the CPS has a short circuit, usually as a result of being savaged by the water pump pulley.
If the CPS is OK (you wouldn't get fuel pressure if it wasn't at least partially alive), then Id expect thins are amiss inside the distributor cover, which you will of had off with the work you have done.
Pull the centre HT lead out of the coil, push the end of a piece of ordinary wire in there, connect the other end of the piece of wire to a spark plug lying on the rocker cover, and crank the engine. The piece of wire should be well away from any metalwork and your fingers.

[steve_k]

I strongly suspect your reading of 0.51 ohms is actually 0.51 kilo ohms = 510 ohms. If it really is 0.51 ohms, then the lead to the CPS has a short circuit, usually as a result of being savaged by the water pump pulley.
If the CPS is OK (you wouldn't get fuel pressure if it wasn't at least partially alive), then Id expect thins are amiss inside the distributor cover, which you will of had off with the work you have done.
Pull the centre HT lead out of the coil, push the end of a piece of ordinary wire in there, connect the other end of the piece of wire to a spark plug lying on the rocker cover, and crank the engine. The piece of wire should be well away from any metalwork and your fingers.

thanks for the input brian, the inside of the dizzy looked to be spotless when it was removed & replaced, but i'll check the contacts anyway,

i'll try that with the spark plug tomorrow, would normal speaker wire be ok to use?

[Brianmoooore]

Any wire will do - just don't touch it. Cap may be spotless, but does it still have the spring and carbon button in the middle?

[steve_k]

well i've just been out & re checked the cps, you were right i had the multimeter set wrong, it's coming back at 510 ohms, i take that is out of the correct range??

also the sheath at the sensor end looks to be split & the wire looks frayed.

[Brianmoooore]

510 isn't far enough away from the expected reading to condemn it. 540 is the normal reading from an OE sensor, but aftermarket could be anywhere in a large range either side of that. Sheath at the sensor end gets brittle with time and heat, but is usually OK if not disturbed and bent too much. I've repaired this before with self amalgamating tape.
Check for sparks direct from the coil in the way I said above before going any further.

[steve_k]

510 isn't far enough away from the expected reading to condemn it. Sheath at the sensor end gets brittle with time and heat, but is usually OK if not disturbed and bent too much. I've repaired this before with self amalgamating tape.
Check for sparks direct from the coil in the way I said above before going any further.

The wire seems to be bent & splayed out & appears loose if you know what I mean?

I'll check for spark at the coil tomorrow.

Don't make any sense as the engine started fine a few month ago before I laid the car up to get some little jobs done.

[steve_k]

right then,

i've tested the coil with a test light across the -/+ terminals of the coil while cranking the engine & it lit up each time,

also tested the coil as you (Brian) suggested with a wire from the centre pole to a spark plug grounded on the rocker cover while cranking then engine again, got a weakish spark which i put down to a weak battery, hooked it up to a booster pack & tried again, again got a spark but not the strongest.

also, to check for fuel i removed the fuel line/hose from the FPR & placed it in a clear bottle & cranked the engine over again, plenty of fuel squirted into the bottle.

also, checked the condition of both the dizzy cap & rotor arm, both look to be in good condition & the points/contacts on each are clean & free of any carbon build up's.

so, so far i know there is fuel, i know there is spark (even if it was weak), i know the timing is correct as it was checked twice (by me & someone else).

as stated above the CPS was reading 510ohms but the wires at the sensor end looked a little bit frayed & worn.

so what else could it be??

[steve_k]

Right all sorted now.

Turns out the ht lead from the coil to the dizzy cap was broken in the rubber cap at the coil end.

Tried another set of leads and it fired up straight away.

[magpie]

hurrah

[steve_k]

hurrah

tell me about it, been doing my head in all weekend but thankfully its sorted (fingers crossed).