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Discussion Starter #1
Hi all
All of a sudden my 156 2,4 jtdm (2004) won’t start at all (4 degrees and wet) : keycode off , all lights behave as usual but when I turn the key, engine rotates but won’t fire. Meanwhile the starter motor runs , the glow warning was blinking so I first imagined a glow issue.
I have the battery a quick charge to make Sure the starter rotates at full speed , no change. The battery is weak however.
I called the tow , who confirmed the glow relay was clicking and even tried to individually bring 12v on each glow before trying to start ; no luck.

My mechanic grabbed the car (I had an appointment with him this morning :D for the CV) : no ODB error at all, gasoline flows ok . A local alfa dealer told him to check the compressions but they are ok. I yet have to confirm (I traveled today) but he managed to start the car . He suspects the RPM sensor.
It was changed like 10 yrs ago iirc , but do you think a faulty rpm sensor would suddenly fail with very few symptoms before ? (In cold times I had a couple of misfires at startup but no big deal and no problems when hot) .

Thanks :)
 

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Possibly a combination of a weak battery no glow plugs and cool damp air. All of those reduce the compression pressure and temperature making ignition of the fuel less likely. I have the same engine and when my old battery was failing last winter it seemed to crank at a good speed but starting was much slower than previously even with working plugs. I think because the battery degrades slowly the reduced cranking speed comes to seem normal, until starting is affected. Add in glow plug failure and cool damp conditions and it fails to start. I would put a new battery on it, get the plugs working and start thinking about the rpm sensor if it still proves obstinate.

(But if tapping/wiggling etc the sensor was what made it start you have your answer.)
 

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What makes him suspect rpm (crank) sensor? Did anything flag up on his diagnostics, no engine rpm signal when cranking etc?
 

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Discussion Starter #4
Hi, I got my car back (CV changed).
The car did not seem to suffer any issue during startups when it was at the mechanic.
I got it on Friday night, started, stalled immediatly and took a second run to start.
I checked multiecuscan this morning and tried a couple of startups while recording/monitoring data (RPM sensor, Voltage)
- RPM values are good, but it might be a binary operation, either it is stuck at 0 and the engine never starts, or it works.
-My original battery (5 y.o) dropped to 8.5 V during startup which is cleary really low AFAIK. (12.3 V at rest)
I changed the battery to a 2 y.o Varta, which was stored for a couple of months, (12.8V at rest before I set it on my car) and the start is OK. It drops only to 9.8V, but it needs a good recharge. Will do some more tests tomorrow.
Wait & see, if it doesn't start I'll be able to quickly identify if the RPM sensor is in cause.
 

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Its the battery. Don't mess about with second hand batteries, a new, correct spec battery is needed. They are sensitive to voltage. When the rpm sensor is misbehaving it does it on warm starts, not cold. The injectors need sufficient rpm to generate the pressure needed to inject, if its slightly down on rpm because the battery is weak it won't start.
 

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Discussion Starter #6
Thanks Hugh :)
There is another point, the ECU voltage reads about 0.5-0.75 V below the battery voltage (ie 13.5 where the battery is 14.1) . I'm suspecting loose grounds or so on, I maybe find them so I can clean.
Do you have such differences ?
 

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Always a good idea to clean those up, the main one is under the battery, clean where it is bolted to the body.
 

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Discussion Starter #8
Hi alfisti,
I noticed a couple of very difficult starts these days, and today, as in Containment zone, I was doing some tests :
- Glow plugs glow properly (20 seconds after the key position on ON, they are still glowing), all 5 of them

But, as the first day, my engine won't start.
I tried using my second car battery to help through poor quality cables, engine is quicker but does not start. THe engine is specifically cold, and, even if MES is messing up, I could see the RPM sensor values non null.
The poor quality cables cannot exclude that my battery just doesn't keep up the voltage as you said, especially when starting.
Regarding EGR, what could I do to make sure it is behaving properly (it is 3 yo). ?

The oddity is that glowing plug light blinking while the engine is not starting. I remember that I had a couple of rough start earlier last year, I cannot remember this light blinking while starting. Nowhere I can see what does it mean, if it even means something (the voltage may mess up everything).

Thanks
(I'll end up trying my wife's battery (a 2.0 D4D Toyota) and buy a new one, but I wanted to avoid any other issue).
 

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Discussion Starter #9
Hi !
Tried the Toyota's battery, no luck.
Voltage drops at 10V (it has 4yo+...) MES disconnects after 2 seconds of starting.
I'm worried about changing the battery. Not really sure that all of a sudden, even a weak battery cannot make the engine start at all. I didn't notice in the forums that the 2.4 jtd was so demanding battery wise :(
 

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Discussion Starter #10 (Edited)
Hi ! some news (I can make a lot of tests, no driving needed, quarantined at home).
I charged twice the battery, which had a 12.9 V at rest, 10.5V while starting (not that great, it has to be replaced for sure) and it seemed to be more prone to start while revving the starter motor.

Then I wanted to check the injector return hose, I disconnected it from the 55180211 (ducting device). I was very surprised that when the contact key is ON, fuel goes from the device to the injector's return hose (?) for 2 secondes. I imagine that there must be some kind of technique to avoid any bubbles ?

Nonetheless, this is while cleaning the mess that I found out that the hose connecting the fuel filter to the HP pump was not totally plugged in. And I was wondering what if it was just an air intake that was making the startup more and more difficult along a weak battery.

I secured it back. It didn't start right away, but 3 tries later it started. That rules out ECU failure or other major failure. MES is working like a charm, I could measure decent injector correction values, good fuel pressure sensor values.
The next day, it started immediatly, twice (didnt happen since at least 2 weeks). The third time it started immediatly, stalled and restarted in 2 seconds. Clearly better, but maybe not over yet :)


Facts:
Fuel pressure sensors seem OK and relevant (270 bar idle, 700 bar+ at 2200 rpm)
Once started, the car never stalled nor has any performance issue
Once hot, it, so far, doesn't have any problem restarting (not RPM sensor I guess)

Questions:
-Would a fuel regulator cause startup issues ? What else, in the fuel injection system would cause no start (besides injector failure)
-Would a single failing injector prevent startup ?
-Why the return hose is getting fuel while the contact is ON ?

Thanks :)
 

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A faulty injector could cause it as rail pressure might not reach enough to allow starting.

fuel in return line when ignition on is normal as in tank pump primes system,the return goes to filter rather than direct to tank for fuel heating purposes. If pressure is built up in filter from tank pump it will escape from open return line.
 
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