Starting problem - 86 Spider Veloce 2.0 - Alfa Romeo Bulletin Board & Forums
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post #1 of 46 (permalink) Old 10-07-2010, 11:11 AM Thread Starter
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Question Starting problem - 86 Spider Veloce 2.0

This is happening randomly. Engine can be cold or hot. It will turn over but not catch. I can wait a minute or so and then it starts right up and runs perfectly.
I have replaced cold start valve with a new unit. However I don't think this comes into play on a warm engine.
I'm thinking the fuel system pressure is bleeding down. The injectors are brand new so I'm thinking there is a bad check valve in fuel supply circuit.
Also I believe that one or both of the fuel pumps act as check valves.

Any ideas would certainly be welcome.
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post #2 of 46 (permalink) Old 10-07-2010, 01:19 PM
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Hows the cold start injector?
Thermo-time switch working OK?

There are no 'check valves' in the fuel feed system.
Both pumps are more or less straight through vane types (you can't pour stuff through them, but they will pass fluid over time, thus line and rail pressure will go down after X time sitting) and the regulator is about as close as you could get to such, but its on the opposite end of the rail. (granted if its bad it can back bleed into the rail, but it'll pull fuel from the return line with it, so no air pockets or the like)

When you turn the key from off to on do you hear the pumps run for 1/2 a second or so?
If so, what happens if you turn the key on and off a few times, then try to start it?
(doing so with the pumps pulsing will pre-pressurize the rail)

If not, you'll need to chase why the pumps don't get that quick activation as they should give a pulse, and then come online steady during the start cycle.

Have you parused the diagnostics as found via the spider l-jetronic diagnostics link in my sig block?




Darren
'84 manufacture ~ '85 MY Spider Graduate

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post #3 of 46 (permalink) Old 10-07-2010, 02:22 PM Thread Starter
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Off hand do you know if both pumps are supposed to be energized with key on ON and car not running?
Now that I think about it this almost has to be an electrical problem as I have had trouble starting car even after it has sat for only a few minutes. I can't believe it could physically lose pressure that quickly.
Also I've recently replaced both main and tank pump and filter. And also ignition switch.
Maybe a bad pump relay??
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post #4 of 46 (permalink) Old 10-07-2010, 02:42 PM
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The pumps are NOT powered on with the key on/engine off.

When you first turn the key to 'on' the pumps will momentarily be powered up but they do not stay on. When the engine is started the drive relay gets a signal from the coil and powers on the fuel pumps. If the engine should stall (say in the event of an accident) then the lack of a coil signal to the drive relay prevents the fuel pumps from continuing to pump.

There is also a 'start' signal (only when the key is turned to 'start') that bypasses the drive relay thus ensuring the pumps pump during cranking. Otherwise it is the drive relay that controls power to the fuel pumps.


- - Eric
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~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
Mebane, North Carolina


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post #5 of 46 (permalink) Old 10-07-2010, 02:47 PM Thread Starter
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Great information.

Many thanks
Warren
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post #6 of 46 (permalink) Old 10-07-2010, 02:53 PM
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Lots more info in the L-jet Spider diagnosis page. Link below.

- - Eric
don't read this
~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
Mebane, North Carolina


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post #7 of 46 (permalink) Old 10-07-2010, 04:12 PM
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Quote:
Originally Posted by trojwl View Post
Also I believe that one or both of the fuel pumps act as check valves.
A standard diagnostic test is to check for fuel system bleed down in engine off condition. A pressure gauge is installed in the fuel rail, engine started (check pressure reading) then engine turned off. Pressure should not drop below spec over x period of time (not sure if Alfa has a spec on this). A 10% drop in less than an hour would not, IMO, be acceptable. Sources for bleed down can be fuel injectors, cold start injector, fuel pressure regulator and check valve in the main fuel pump.

Jim

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post #8 of 46 (permalink) Old 10-07-2010, 04:28 PM
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There is a spec, but I'll be damned if I can find it right now.
I think its buried in the board somewhere....

I wanna say its a shade more than 10% in an hour though, but that's based on a really vague memory. (the regulator remains open a bit regardless of the engine running, so bleed off to some degree or another is inevitiable. More important that it hold proper pressure when running than keeping it up overnight when not IMO)




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'84 manufacture ~ '85 MY Spider Graduate

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post #9 of 46 (permalink) Old 10-07-2010, 05:02 PM Thread Starter
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Smile Thanks

Thanks all for some great info.
First thing I'm gonna do is run a wire from the fuel pump power leads to the passenger seat. I will have multimeter in hand. When I have this problem I can instantly see if pump(s) are even being energized during starting. If not I'll work backwards. If so, then I start checking the physical components.

Also, I have 32 years of instrumentation and process controls experience in a major power generating station so I kinda know how to do things like this. And boy am I learning more and more about this car everyday.

I'll say one thing about the Italians - they sure can cook.

Also, anyone know where I can get my hands on a circuit diagram with wire colors? I have the white factory manual that I'm sure most of us own. Let's just say I've seen better manuals.

I am so glad I joined this forum. Great people and great info!
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post #10 of 46 (permalink) Old 10-07-2010, 05:05 PM
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Is this the spec we seek?

Flow at inlet end of rail with zero pressure applied: 1.5~2 liters per minute / .33~.44 gallons per minute

Or is that 'zero pressure' anticipated flow w/zero manifold pressure at/on the regulator?
(implying the regulator has an inherant bleed by regardless)


Anywho, I found it buried in with some stuff dealing with the feed system, but not in the L-jet book. There's only a couple references I found on the BB and they weren't specific #'s wise, but suggested somewhere between 1/2 and hour to an hour was in the range of majority to full pressure bleed down in the L-jet systems.

Still, I know I've seen somewhere a very specific X pounds pressure loss over Y amount of time from shut down, and it's starting to get up my nose that I can't readily find it LOL




Darren
'84 manufacture ~ '85 MY Spider Graduate

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post #11 of 46 (permalink) Old 10-07-2010, 05:07 PM
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Quote:
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Also, anyone know where I can get my hands on a circuit diagram with wire colors?
Most certainly.
Ask that nice papajam guy and he'll be able to hook you up with a full color, fully laid out and actually useable work of art that he generates for us lesser folk.

When not in use they are suitable for framing.




Darren
'84 manufacture ~ '85 MY Spider Graduate

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post #12 of 46 (permalink) Old 10-07-2010, 05:11 PM Thread Starter
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Papajam, are you listening???

Man, that would be GREAT!! - and much appreciated!

Warren
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post #13 of 46 (permalink) Old 10-07-2010, 05:18 PM
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Teaser shot of the 85 diagram to get you moist.



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post #14 of 46 (permalink) Old 10-07-2010, 05:39 PM Thread Starter
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I want!!!!!!!!!!!
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post #15 of 46 (permalink) Old 10-07-2010, 07:36 PM
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Quote:
Originally Posted by Tifosi View Post
Ask that nice papajam guy and he'll be able to hook you up with a full color, fully laid out and actually useable work of art that he generates for us lesser folk.

When not in use they are suitable for framing.
I took a digital copy (on one of those flash drive thingies) to an office supply store. I had them print me an 11"X17" color copy then plastic laminate it. Cost about five bucks. It is great for the garage as even greasy fingerprints wipe off easily.

- - Eric
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~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
Mebane, North Carolina


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