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post #1 of 18 (permalink) Old 07-30-2019, 02:47 PM Thread Starter
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Angry S4: Spark, Fuel and Air

I'm over my head on a no start problem.

This started a couple of weeks ago when the car died just as I arrived home, very strange, but a few tests confirmed there was no spark and the coil was the culprit. I replaced the coil, charged up the battery (11.4V cranking), and still no start. I confirmed there was now a spark and smelled gas when I pulled a spark plug. So that leaves air and I started checking all the intake hoses and the only bad hose I found was on the relay (what does this do?) on the fender that's switched by vacuum off the intake manifold. I'd already replaced the hose from the intake but the one along the fender was also torn so I replaced that. Still no start, I get one cough and then nothing.


I also checked the flap in the airbox and that was closed and moved freely.

Is smelling gas when the plug is pulled enough to eliminate the fuel pump and system?


What am I missing?


Apologies to fans of Oil, Salt, Acid and Fire.

Mitch
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post #2 of 18 (permalink) Old 07-30-2019, 04:43 PM
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Repeated unsuccessful starting attempts can/will foul the spark plugs making it harder & harder to start (thus compounding the spark plug fouling). If you are now certain there is energy being delivered to the spark plugs (IOW the new coil fixed the original problem) then I suggest replacing the spark plugs. Crank it over for a minute with the spark plugs removed to clear out any flooding. Be sure to re-attach the spark plug wires in the correct firing order.

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post #3 of 18 (permalink) Old 07-31-2019, 12:21 AM
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Quote:
Originally Posted by MitchW View Post
... and the only bad hose I found was on the relay (what does this do?) on the fender that's switched by vacuum off the intake manifold. I'd already replaced the hose from the intake but the one along the fender was also torn so I replaced that. Still no start, I get one cough and then nothing....
that "relay" is a solenoid switch (#14). the ecu tells it when to open to allow fumes from the charcoal canister (#18 hidden inside the fender) back into the engine intake to be burned up. It won't affect a no start, but can affect smooth idle.

what hose 'along the fender' do you mean?

so you are 100% sure you now have spark at the plugs?

as Eric says remove all plugs and spin the starter a few times in case you've flooded the engine.

What I do in case you have caused fuel wash (multiple no start attempts have washed the bores with fuel) is to also squirt some fresh oil down the bores....leave a while, then put plugs back in (cleaned, or new whatever!) and try start.

Personally I don't see the coil as the culprit...."driving along and the car just died"...but there you go. Have you tested this 'bad' coil, primary and secondary resistances?

If you have spark and clean plugs and and it still won't fire, I'd be looking at fuel pressure regulator (#7)
Check the small vacuum hose on top has no raw fuel in it, if it does, it's shot.
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post #4 of 18 (permalink) Old 07-31-2019, 06:43 AM Thread Starter
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Thank you.

15 - Fuel Vapor intake tube. I had a similar no start a month ago and replaced the hose between the intake and the solenoid which fixed it so it seemed like a good place to look. Either way I've replaced both leaky hoses so that's not the problem.

After determining no spark I tested the coil with VOM and found no continuity on the secondary coil.

I used my timing light to make sure there was a spark. The spark plug I removed to check for gas fuel didn't look fouled but I wasn't looking that closely.

It feels like a vacuum leak to me but I can't find it. I took apart and inspected all the hoses and connectors from the air intake to the intake manifold.

I'm open to suggestion.

Mitch
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post #5 of 18 (permalink) Old 07-31-2019, 07:02 AM
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Quote:
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The spark plug I removed to check for gas fuel didn't look fouled but I wasn't looking that closely.
It doesn't take much. Either clean or replace the spark plugs to eliminate them as suspects.

- - Eric
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- -~ 1981 GTV-6 ~
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post #6 of 18 (permalink) Old 07-31-2019, 07:41 AM
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your car would start with a vacuum leak, it just wouldn't idle nicely.

you have a no-start and that can only be fuel, spark or compression.

you checked spark with a timing light?
never done it like that (so just asking)...would that tell you if the spark was good?
I pull a lead and stick a clean used plug on the end...nice crisp blue spark and I'm happy to move on to the next thing....

you smell fuel, but that does not mean you have proper fuel pressure - check the FPR, as above and if no raw fuel in the vacuum hose (a good sign), then clamp off the return line under the FPR and try to start like that.

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #7 of 18 (permalink) Old 07-31-2019, 08:11 AM Thread Starter
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Before replacing the coil I'd tested by pulling a plug and checking for spark but I was being lazy and figured the timing light would show it just as well. Of course I ended up pulling a plug anyway to check for fuel.

The fuel pressure was one of my remaining concerns so I'll check the FPR next.

Mitch
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post #8 of 18 (permalink) Old 08-04-2019, 01:10 PM Thread Starter
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Took a while to get back to it but I checked out the FPR and it seemed okay. No fuel in the vacuum hose and blocking the return line didn't help. I again pulled a plug and it didn't look to bad and got a nice spark. Anything else I should check?

Mitch
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post #9 of 18 (permalink) Old 08-04-2019, 01:51 PM
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You might want to test the crank sensor. Sometimes they die halfway. They give spark just not at the right time.

1969 1750 Spider Veloce w/dual webers, 1969 1750 Berlina, 1971 1750 Spider Veloce w/ dual webers, 1985 Spider Veloce 23,000 orig. miles, {Two} 1986 Spider Veloces, 1987 Spider Veloce bought new, 1988 Quadrifoglio, 1991 164S, Plus several more. I think they are breeding.
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post #10 of 18 (permalink) Old 08-05-2019, 01:32 AM
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test for fuel delivery.
remove hose coming up to the back of the fuel rail - have someone crank the starter (jam jar at the ready or just some rags to catch fuel) - check for a good steady flow.
yes? pumps are working and signal is there, but maybe injectors are not firing or are clogged.

no fuel at rail? check both pumps by applying 12V direct to them.
pumps don't work when jumped? - bad pumps
pumps run when jumped? - check fuel relay (or swop horn relay (from drop-down fuse box) in place of fuel relay (under rear shelf, near ecu)
retest.

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #11 of 18 (permalink) Old 08-20-2019, 03:14 PM Thread Starter
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I'm having second thoughts about whether I was getting fuel so I decided to see if the in tank fuel pump was getting any juice. The problem is there are 3 white wires and one black (ground). Two of the white wires have some voltage when the ignition is turned on so I'm assuming they're for the fuel sender. The middle wire has a plastic sheath and had 0 voltage with the ignition on as well as when trying to start. Does this sound like no juice for the fuel pumps?

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post #12 of 18 (permalink) Old 08-21-2019, 12:35 AM
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Quote:
Originally Posted by MitchW View Post
I'm having second thoughts about whether I was getting fuel so I decided to see if the in tank fuel pump was getting any juice. The problem is there are 3 white wires and one black (ground). Two of the white wires have some voltage when the ignition is turned on so I'm assuming they're for the fuel sender. The middle wire has a plastic sheath and had 0 voltage with the ignition on as well as when trying to start. Does this sound like no juice for the fuel pumps?
3 white wires?...well that is not right. either they are very faded or someone has been chopping wires about back there (possible earlier problem?)

the only wires that feed the in-tank pump are the black (ground) and the pink/white wire (powered when cranking)

the fuel sender wires are the white/black and the purple (or mauve, I suppose)

you could run a separate ground to the ground terminal just to eliminate that as a problem, but yes if you are getting no power when cranking at the pump, then there is probably a bad relay.
To test the pump (I'd do this first) is working, just run two wires direct from the battery to that black terminal and to the pink/white terminal....you should hear the pump hum along nicely.

4 main relays are under the parcel shelf. The fuel relay is the simple relay w/o a fuse (as opposed to the 2 relays with a fuse and the one relay with a red-stripe)...pin #87 is feed for the pumps. To quickly test this relay, remove the horn relay (1st relay, top left in drop down fuse box) and put it in place of fuel relay. (or with an Ohmmeter, test between pin#85 and #86 of relay and you should read about 70-80 Ohms)

edit: oops I'm repeating myself....
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Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.

Last edited by spiderserie4; 08-21-2019 at 12:47 AM.
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post #13 of 18 (permalink) Old 08-21-2019, 07:24 AM Thread Starter
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I checked the ordinary relays and they were all around 70 ohms. The one I'm not sure about is the red stripe relay which I replaced with the Land Rover alternative from ebay. Of course it was a substitute part number and when I tested for resistance got ~1700 ohms which wasn't inspiring.

The wires are probably favored and don't look modified though the pink fuel pump power line does look thinner.

Can I put in a jumper at one of the relays to power up the fuel pumps? I read jumpering terminals 87 + 30 will do it but they didn't specify which relay.

Mitch
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post #14 of 18 (permalink) Old 08-21-2019, 07:51 AM
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Can I put in a jumper at one of the relays to power up the fuel pumps? I read jumpering terminals 87 + 30 will do it but they didn't specify which relay.
That works on the L-jetronic spiders on the big Bosch relay, but I have neither heard nor read that it is the same for the S4. So I'd be a little worried to try it, personally.

Is the fuse (15A) on the Auxiliary motronic relay good?...if that is blown then no power to fuel relay.

Edit: maybe someone with more electrical experience can tell you, looking at the relays schematic here:
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Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.

Last edited by spiderserie4; 08-21-2019 at 07:56 AM. Reason: add schematic snippet
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post #15 of 18 (permalink) Old 08-21-2019, 12:00 PM Thread Starter
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I'd like to find another way to jump the fuel pump because I can't get under the car right now.

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