164 24v poor running - Alfa Romeo Bulletin Board & Forums
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post #1 of 13 (permalink) Old 02-11-2018, 09:50 AM Thread Starter
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164 24v poor running

Hi everyone,
My 164 24v QV started to run rough a few weekends back. Started off with just an intermittent hick-up / lack of power at around 3000rpm but would then be fine if you dropped it back down to idle. I spotted some leaking fuel on the rubber supply hose to the fuel damper so i have replaced all of the old rubber hoses under the bonnet and thought that would solve the problem.

I then did the fuel system pressure check as described in the manual and got 43psi at idle with the vacuum hose to the regulator disconnected (manual says it should be 42 - 47psi), then i reconnected the vacuum hose and it only dropped to 41 psi and not by 7.3 psi as per the manual. So i am thinking that could be part of the problem - but not sure what to look for next?

Other symptoms are:
1) Engine revs fluctuate if you hold it at a steady 2500 rpm for example.
2) Sometimes it dies completely and the fuel gauge drops to 20psi and won't go back upto 41
3) Sometimes with 41psi on the gauge it still won't start
4) Cam angle sensor error code is showing on the diagnostics 1255

Does anyone have any ideas? I did the cambelt before christmas but don't think it is timing related as it runs fine sometimes and the symptoms seem like they are fuel related.

Thanks for your help
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post #2 of 13 (permalink) Old 02-12-2018, 05:39 AM
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Do another fuel pressure test with test gauge installed in series to hose going to fuel damper inlet near rear of front head on 24v model not at fuel pressure regulator fuel return to tank hose near rear head.

Now remove fuel pump relay (non-red strip) on top radiator support, insert jumper wire pin 30 pink power wire socket to pin 87 pink-white fuel pump wire in relay socket. Now turn on key but do not start engine. Check fuel pump pressure on gauge should get 45-50 psi. Turn off key and see if system holds pressure.

Report your findings.

Ciao, Alfisto Steve
Virginia Beach, VA
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Alfa Semi-Daily driver: USA model - BB2 1991 164S Black Beauty II ALFISTO [U]

[U] BB1 1991 164L w/S engine and A/T now excess to inventory [U]

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post #3 of 13 (permalink) Old 02-12-2018, 11:32 AM Thread Starter
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Hello Steve, thanks again for your quick reply.

Firstly I should have explained better, my gauge is in series to the hose going to the fuel damper.

I carried out the test you suggested and I get 46psi with the jumper wire in and the key turned. This drops immediately to 42psi when I turn the key off and from there it very gradually drops away. Is this correct?
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post #4 of 13 (permalink) Old 02-12-2018, 12:21 PM
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Quote:
Originally Posted by Ahollis View Post
Hello Steve, thanks again for your quick reply.

Firstly I should have explained better, my gauge is in series to the hose going to the fuel damper.

I carried out the test you suggested and I get 46psi with the jumper wire in and the key turned. This drops immediately to 42psi when I turn the key off and from there it very gradually drops away. Is this correct?
If is decays away as in towards 0 psi you possibly have cracked leaking hoses inside fuel tank and/or leaking ball check valve on top of fuel pump which are located inside fuel tank.

The pressure usually will not drop to 42 right away but you could have a weak diaphragm in fuel pressure regulator that will only had pressure to 42 psi before hoses and check valve start to bypass. If you do the key on plug in/pull out jumper be sure fuel can't spray near jumper. Better to have a helper at ignition with stop watch.

I have a new non-Bosch pressure regulator that will only give about 43 psi with pump running so have not installed it.

Now another test is a pump fuel flow test. I usually use a quart mayo jar or even a beer bottle and do a 15 second flow test to see if you get over 8 oz. in 15 second.

Ciao, Alfisto Steve
Virginia Beach, VA
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Alfa Semi-Daily driver: USA model - BB2 1991 164S Black Beauty II ALFISTO [U]

[U] BB1 1991 164L w/S engine and A/T now excess to inventory [U]

Daily driver and parts hauler but not car hauler 2004 Jeep Grand Cherokee Overland 4.7L H.O. V-8

"A day without an Alfa whine is like a day without sunshine"

Last edited by Alfisto Steve; 02-12-2018 at 12:23 PM.
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post #5 of 13 (permalink) Old 02-12-2018, 07:54 PM
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Must have > 41 psi to run. Check your fuel pump hoses as Steve says. If never changed they are “past due”!!

74 GTV with 10548's and Ingram pump
71 Spider 1750 BOMBER ; 1995 LS 78K tight fast car
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post #6 of 13 (permalink) Old 02-17-2018, 08:38 AM Thread Starter
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Thanks for your replies,

I did some further investigation today and this is what i have found:

1) The engine starts and idles roughly at 42 psi fuel pressure
2) When you press the accelerator gently the fuel pressure drops to 38/39psi - I would of thought it should rise?
3) When you lift off the accelerator the fuel pressure rises to 40/41psi but doesn't return to 42psi. The engine seems to tick/click, is this a sign of it knocking?
4) When you switch the engine off the fuel pressure now drops to 0psi within 10 seconds

Is this a sign of the tank hoses needing attention or could it be the regulator?
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post #7 of 13 (permalink) Old 02-17-2018, 09:23 AM
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Tank hoses first thing. Easiest to do cheapest and need to rule out; plus if you haven’t done it yet then it’s a pending item.

74 GTV with 10548's and Ingram pump
71 Spider 1750 BOMBER ; 1995 LS 78K tight fast car
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post #8 of 13 (permalink) Old 02-24-2018, 09:15 AM Thread Starter
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Hello,

I changed the fuel pump hoses and then did a fuel flow test as Steve suggested and i get 23 oz in 15seconds at the pump in the boot and the same in the engine bay. Still runs rough

One thing i have noticed is that on the initial start up where the injection system gives a small blip of throttle before it settles to idle is that during that blip it runs well and then it settles down to its rough idle.
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post #9 of 13 (permalink) Old 06-24-2019, 10:25 AM
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Exactly the same symptoms. Did you solve it?
Thanks Tim
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post #10 of 13 (permalink) Old 06-24-2019, 10:53 AM Thread Starter
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I sure did! Rear bank had jumped a tooth on the cambelt and the unrestrained lead from the crank sensor had been chewed slightly by the cambelt. Both of which were my fault, but once rectified it ran beautifully and still does today. You live and learn!
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post #11 of 13 (permalink) Old 06-24-2019, 11:52 AM
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why do you think it jumped a tooth. Belt tension?

164LS 1994
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post #12 of 13 (permalink) Old 06-24-2019, 12:02 PM Thread Starter
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It was belt tensioner, I had not done a cambelt on one of these before and it was my local helpful Alfa garage that pointed out what I did wrong.
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post #13 of 13 (permalink) Old 06-24-2019, 12:23 PM
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what had you done wrong? Pray tell...I like to learn from other peoples mistakes
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