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Discussion Starter #1
A few months ago the car stalled on me as I was accelerating, entering the freeway. Engine acted as though it ran out of gas or the ignition was turned off - it just died, no sputtering at all. I had just replaced the battery and had driven it for a few consecutive days (car is not used daily).

The main fuel pump had been very noisy for a while, and I thought that was the problem. I replaced both fuel pumps and filter (in tank pump was dead). Car will not start, however.

Here are some things I have checked.
Fuel tank is full.
Battery has 12.65V after charge.
Air flow meter has 360 Ohms across pins 3&4 and 104 Ohms across pins 2&4.
Fuel pumps appear to be working.
All of the relays near the ECU appear to click when ignition in MAR position.
Battery voltage observed at fuel injector when ignition in MAR.
Self diagnosis of ECU was 4444 = "no recognized malfunction"
Observed spark when plug placed on valve cover.

Not sure how to test the following:
Accelerator throttle switch.
Revolution and timing sensor.

Any suggestions are appreciated. Thank You.
 

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as you have spark, I am not sure there will be a problem with the crank position sensor.

To test it anyway, undo the bosch 3-pin plug (located up near the windscreen washer bottle filler cap) and test resistance between one of the outer pins and the middle pin of the plug on the cable coming from the sender itself you should get about 500-600 ohms (I get 520 ohms on my S4, as a reference)
Note: one outer pin and centre gives a resistance reading, the other outer and centre gives no reading...so test both ways, to be sure you have the right pair!

The accelerator throttle switch (TPS: Throttle Position Switch)
Test: this should click just as you manually move the throttle off its end stop.
If it doesn't it can be adjusted by undoing the one fixing screw that sits in the 'oval' slot, and turned clockwise until it does click when throttle 'just' lifts off its end stop. Alternatively you can test this with an ohms tester between pins #18 & #2 (the top two pins) where the reading will go from no resistance to infinity. But the click test is usually the easiest, well, as long as your hearing is OK.

Does it even try to start/catch, or there is nothing at all, just turns over?
Have you tried with starter fluid?

Have you checked you are getting fuel?
Remove main fuel hose entering the left hand side of fuel rail and stick some rags down there and have someone crank the starter - Does fuel pump out when you crank?

Has small vacuum hose from inlet plenum to fuel pressure regulator fallen off, or is split/blocked? And there's no signs of raw fuel in this vacuum hose (which could point to a leaking regulator)?
 

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Discussion Starter #3
as you have spark, I am not sure there will be a problem with the crank position sensor.

To test it anyway, undo the bosch 3-pin plug (located up near the windscreen washer bottle filler cap) and test resistance between one of the outer pins and the middle pin of the plug on the cable coming from the sender itself you should get about 500-600 ohms (I get 520 ohms on my S4, as a reference)
Note: one outer pin and centre gives a resistance reading, the other outer and centre gives no reading...so test both ways, to be sure you have the right pair!

The accelerator throttle switch (TPS: Throttle Position Switch)
Test: this should click just as you manually move the throttle off its end stop.
If it doesn't it can be adjusted by undoing the one fixing screw that sits in the 'oval' slot, and turned clockwise until it does click when throttle 'just' lifts off its end stop. Alternatively you can test this with an ohms tester between pins #18 & #2 (the top two pins) where the reading will go from no resistance to infinity. But the click test is usually the easiest, well, as long as your hearing is OK.

Does it even try to start/catch, or there is nothing at all, just turns over?
Have you tried with starter fluid?

Have you checked you are getting fuel?
Remove main fuel hose entering the left hand side of fuel rail and stick some rags down there and have someone crank the starter - Does fuel pump out when you crank?

Has small vacuum hose from inlet plenum to fuel pressure regulator fallen off, or is split/blocked? And there's no signs of raw fuel in this vacuum hose (which could point to a leaking regulator)?
Thanks Dom.

I measured 545 Ohms across the two pins of the crank position sensor, so I guess that is OK.

The TPS checks out OK also, clicking is present, and correct readings at minimum and maximum throttle opening measuring two different sets of pins.

Vacuum hose from plenum to fuel pressure regulator appears in good condition - no cracks or splits, etc.

Next I will remove the fuel hose from the fuel rail to see if I'm getting enough fuel. I expect under normal conditions there should be some pressure in the fuel line.
 

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Hold your hand on the main pump and have someone crank the car over. apply ebrake and put in neutral before doing this. If you don't feel the pump running you have a wiring problem. Have you checked the fuel pump fuse thats under the panel behind the passenger seat?
 

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the 92 (Motronic) doesn't have an inline fuel fuse under the rear panel like the S3 L-jet.

If you find in fact the new pumps are not working, then check the fuel pump relay under the rear shelf (of the 3 identical ones, it is the one 'without' a fuse)...swop it with the horn relay (first left, top row - in drop down fuse box)

you get battery voltage to the injectors, but do they pulse on cranking? You'll need a noid light for that, I think.
 

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Discussion Starter #6
I got under the car to feel the main fuel pump, and the pump appears to be running while the starter is cranked. I will try testing the fuel pressure at the fuel rail. The manual says it should be about 40-45 psi.
 

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Discussion Starter #7
I measured fuel pressure 40-50 psi while cranking the starter. There were a couple of short pops while cranking the starter. I will recharge the battery and try some starting fluid.
 

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you have spark (re-check that each time you do some work, in case that too has gone!)
you have fuel pumps running
you have fuel pressure at the rail

I can only think the injectors are not pulsing (hence the Noid test light I suggested), in which case you have to look again at the relays, fuses, wiring etc.

Starter fluid will soon tell you (it needs to be introduced without an air leak, somehow...)
 

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...................any success, news....??

:whistling:
 

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This is puzzling. Air, fuel, and spark? Should fire up assuming timing hasn't been thrown off somehow.

Are you 100 percent positive you have spark from the coil?
 

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Discussion Starter #11
Thanks for asking - been busy lately and haven't done much. Tried the starting fluid, but had no noticeable effect. Really wondering whether I am getting good enough spark. What do you suggest as a reliable test? Previously I took out one plug and duct taped it to the valve cover.

Coil, plug wires, cap, etc. are all original. Car has about 120,000 miles. Cap has some pitting on the 4 terminals, but spring loaded center terminal seems OK.
 

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Wow!

Thanks for asking - been busy lately and haven't done much. Tried the starting fluid, but had no noticeable effect. Really wondering whether I am getting good enough spark. What do you suggest as a reliable test? Previously I took out one plug and duct taped it to the valve cover.

Coil, plug wires, cap, etc. are all original. Car has about 120,000 miles. Cap has some pitting on the 4 terminals, but spring loaded center terminal seems OK.
Wow dude I am having exact the same issue with my 86 spider. All symptoms are exactly as you have described it I mean exactly! Been working on it for 3 months with no luck! So taking it to the shop next week! Good luck and keep us posted!
 

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Discussion Starter #13
This is puzzling. Air, fuel, and spark? Should fire up assuming timing hasn't been thrown off somehow.

Are you 100 percent positive you have spark from the coil?
Today I checked spark again. Removed all four plugs and observed strong spark (white in color) from all four plugs.

Problem must be with the fuel side. Fuel pressure regulator? Bad gasoline? Note that the car has been sitting a few months.
 

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Discussion Starter #16
An update to the no-start...

After several months sitting in the garage, I had the car towed to the mechanic. He diagnosed it the next day - no compression. He also discovered the cam timing had jumped and probably the valves were bent. Perhaps I should have suspected no compression because of the weird sound when cranking the engine, but I'm not a professional mechanic.

The mechanic pulled the head and confirmed all exhaust valves are bent. His suspicion is that the large sprocket on the intermediate shaft had slipped and messed up the cam timing. He also said that on the later cars this sprocket is pressed on, rather than keyed. He claims to never have seen this happen on a street car. I'm surprised that such a critical component would be pressed on.

I decided to have him rebuild the engine since the bottom end has about 125K miles on it. I'm picking it up tomorrow, and will try to get more details.

I hope this update is useful to someone, and I hope none of you experience this failure on your cars.
 

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The mechanic pulled the head and confirmed all exhaust valves are bent. His suspicion is that the large sprocket on the intermediate shaft had slipped and messed up the cam timing. He also said that on the later cars this sprocket is pressed on, rather than keyed.
I hope this update is useful to someone, and I hope none of you experience this failure on your cars.
sorry to hear that.
it is rare, but there have been cases....and it is not dependant on whether keyed or pressed on sprocket....this thread is about a keyed on failure:
http://www.alfabb.com/bb/forums/engine-repair-diagnostics-rebuilding/166587-broken-timing-chain-sprocket.html
 

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I would try dumping a bottle of injection cleaner in the tank along with 4-5 gallons of fresh fuel. Also, try pulling your plugs after cranking to see if there is any fuel on electrode.

Good luck
 

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I would try dumping a bottle of injection cleaner in the tank along with 4-5 Gallons of fresh fuel. Also, try pulling your plugs after cranking to check for fuel on electrode tip.

Goog luck
 

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After several months sitting in the garage, I had the car towed to the mechanic. He diagnosed it the next day - no compression. He also discovered the cam timing had jumped and probably the valves were bent. Perhaps I should have suspected no compression because of the weird sound when cranking the engine, but I'm not a professional mechanic.

The mechanic pulled the head and confirmed all exhaust valves are bent. His suspicion is that the large sprocket on the intermediate shaft had slipped and messed up the cam timing. He also said that on the later cars this sprocket is pressed on, rather than keyed. He claims to never have seen this happen on a street car. I'm surprised that such a critical component would be pressed on.

I decided to have him rebuild the engine since the bottom end has about 125K miles on it. I'm picking it up tomorrow, and will try to get more details.

I hope this update is useful to someone, and I hope none of you experience this failure on your cars.
I have seen it several times over the years. It can happen when the chain is over tensioned. i.e. someone used a pry bar to force the chain tensioner out then locking it down while still prying on the tensioner.
 
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