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Discussion Starter #1
Hi AO's. I'm back in the ownership of a Alfa 33 :thumbs:. It's got lowered suspension and is a real joy to drive but it's got a fault that i could do with some help with.
What it's doing is the oil light is coming on when the car is at full temperature and when the engine is idling, the light only flickers on and off while the on idle as soon as you pick the rev's up the light goes out.
Also it run's very rich from cold, I've had a few 33's before this and i can say this run's richer than any of my other ones.
I have checked the oil and it's clean but i can slightly smell fuel in it so I'm thinking do an oil change next week as i don't intend to use the car until then and then back off the fuel mixture.

Any thought's on this would be appreciated.

Thanks.

From Ash :)
 

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hi mate, i would get the carbs looked at to sort out the rich running,
the oil sounds like its got a bit too thin, either due to age or the petrol getting to it - due to running rich,

get your carbs sorted and fresh oil in there and it should be good to go mate
 

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If you have Jetronic injection, maybe the spring preload of the airflow meter vane has been altered
(reducing the spring preload of the AFM vane will result richer mixture in the whole RPM range, especially
@ cold engine when the lambda control is not enabled), or someone might played with the open-loop mode
mixture screw. This screw originally sits behind a sealing cap on the Jetronic control unit, if the cap is
missing or tampered, the open-loop mixture setting may be incorrect.
 

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Discussion Starter #5
Hello.

Thanks for your help LoneWolf33. The sealing cap does look like it has been tampered with on the airflow meter control unit so that must be why it's been running rich.
Is it common to get a slight fuel ingress into the oil in that case?
If so that could have thinned the oil like Kemmatic said.

I thought i would ask about it on here though because i was thinking it could be the oil pump or oil pick up (filter?) from the sump and getting worried about the potential cost's involved.

I will get it looked at by a mechanic to sort the mixture and update this thread.

Thanks to Kemmatic as well. I love the sound of twin 40DCOE carbs on a boxer engine, especially with K&N air filters on for the added induction noise :cool: but mine has fuel injection.

Cheers.

Ash. :)
 

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IMHO some fuel ingress into the oil is normal and unavoidable, for example
during the engine cold startup and warmup phase. But when the oil approaches / reaches
the operating temperature, most of the fuel ingress will evaporate (and through the
crankcase ventilation will be sucked into the cylinders), but leaves some petrol smell behind.

As SteffenJ mentioned the hot viscosity of the old oil can affect the oil pressure at idle.

To rule out the warning light sender and the oil pump wear, check the oil pressure with a
workshop gauge, the pressure should be at least 1 bar (14.5 psi) with hot oil @ 900 RPM.
Under 900 RPM the delivery curve of the oil pump drops rapidly (the idle RPM should be checked
with an external tachometer, because the one in the dash is not too accurate). In some cases
the manual idle speed adjuster is not allows to set the speed to the recommended value @ hot
engine.
 

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Discussion Starter #8
Hello.

Thanks for the replys.
I have had the car for just over a month now. The oil looks good it's still more green than brown in colour.
Another thing it does that may be relevant is that sometimes from cold start it will only run on three cylinders until the engine warms up, it always runs very rich from cold start and stinks of fuel from the exhaust so running on three makes it so much worse:(.
I have checked the spark plugs and one looks slightly damaged (on the cylinder that's intermittently not working) so i have some new Gold Lodge ordered and on the way and that should cure the problem.

Thank you LoneWolf33. of course, that make's a lot of sense about fuel ingress and how it will evaporate as the oil heats up.
Good advice too about how to rule out light sender and fuel pump. I will get that checked out too.

Thanks again.

Ash.:thumbs:
 
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Good advice from Lonewolf. If comp test is good on all cylinders then may i suggest a new pressure sender as it's cheap (approx £7) and most probably your problem. I had exactly the same problem and after a lot of hassle dropping the sump and inspecting the pump it turned out to be the sender!
 

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Discussion Starter #11
Hello,

That sounds interesting Lee16v, where is the oil pressure sender located? and what does it look like?
I'm sure i have good compression on all cylinders because when the engine is warm it runs smooth and has good performance. I will check when i fit my new plugs to be sure though.
Thanks for your help.

BigAl33, no i haven't checked the coolant temp sensor. The stat is good and temperature is OK. Why do you suspect temp sensor? and how would you recommend i check it?
Thanks for your suggestion.

Cheers.

Ash.:)
 

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I had a 16v which used to run rough when cold, I know the ECU's are different but I guess they work the same. When there was no signal from the CTS the ECU goes into safe mode and over fuels, very noticable when cold as no Lambda correction is used and cold fueling is added.
Test the CTS with the multimeter set to 20 kOhm, should get, that's if your 8v uses the same sensor.

-10C = 9 kOhm
0C = 6 kOhm
+10C = 3.8 kOhm
+15C = 3 kOhm
+20C = 2.5 kOhm
+25C = 2.1 kOhm
+30C = 1.7 kOhm
+40C = 1.2 KOhm
+60C = 600 Ohm
+80C = 330 Ohm
 

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The 8V and 16V versions are using the same ECU coolant temperature senders.
On the 8V version the sender is located in the rear side of the RH intake port.
The sender has light blue connector facing towards the bulkhead.
A suggestion: instead measuring on the hardly accessible sender terminals directly,
it might easier to check the resistance in the Jetronic ECU connector, between
pins 5 and 8 (see the attached figure).
 

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Ash,

The oil pressure sender will be either by the oil filter or in the middle of the block at the back (bulkhead end). Position varies between cars (not sure why) but will be recognisable as a 19mm nut with a bakolite type dome on top with a single flat blade terminal fitting.

Lee.
 
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