'83 Spider - Fuel Drain Back? - Alfa Romeo Bulletin Board & Forums
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post #1 of 29 (permalink) Old 07-15-2017, 11:58 AM Thread Starter
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'83 Spider - Fuel Drain Back?

Can anyone think of a scenario where fuel would drain back into the gas tank after the car has been shut down and sat for a while?

There are times where I experience an "excessive crank" after the car has been sitting; then the car starts and simply purrs @ 800 rpm. Kinda odd. The only model I can come up with is fuel drain back or fuel line de-pressurization. There are no external fuel leaks. Fuel pumps, FPR, and fuel filter are new. Fuel return line is clear. Fuel line to fuel rail is clear. After the initial "excessive crank" finally starts, I can shut it down, then have an immediate re-start with no problems what so ever.

Opinions? Wild speculations welcome.............
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post #2 of 29 (permalink) Old 07-15-2017, 12:21 PM
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I think this is common when the car has been sitting for an extended period. I usually turn the ignition on and let the electric fuel pump run for a few seconds. Sort of builds up the pressure lost by sitting.
Cheers, Jon

Present:
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post #3 of 29 (permalink) Old 07-15-2017, 12:47 PM
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odd......I can leave my car (S4) for weeks and it starts right up, a few cranks is enough, and it is not that different to an S3.

Next time you expect it to happen, pinch the fuel return line from the FPR, and see if it starts easier.

maybe the vacuum hose for the FPR is slightly split? so that at initial start up the pressure regulator is not getting its required vacuum pull?
I suppose you got a bosch FPR, there have been a few reports on here of aftermarket ones failing.
(well, you said wild specultions welcome)

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 #4 of 29 (permalink) Old 07-15-2017, 01:19 PM
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If all systems are working properly the fuel pumps (there are two) will only operate under two conditions - the engine is running or the key is in the 'start' position. Simply turning the key to 'on' will only power up the pumps for a moment.

Next time the car has been sitting for a while, try this - cycle the key on, off, on, off, on, off then on & start. If that makes it start quickly then go looking for the reason the system needs to be 'primed'. But, I think that normally it doesn't hold much if any fuel under pressure for longer than a few minutes or maybe an hour or so. I'd wonder if there is another reason it needs longer cranking when it hasn't been run for a while - poor operation of Cold Start Injector for example. Or maybe the car is just upset you haven't taken it for a ride for so long...

- - Eric
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~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
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post #5 of 29 (permalink) Old 07-15-2017, 01:49 PM
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There's a check valve in the main fuel pump. Between that and the fuel pressure regulator, it should hold pressure in the rail with the car off. You may be losing pressure at one or both ends, or have an injector that's leaking with the car off.

You'd need to hook up a fuel pressure gauge and monitor/test to troubleshoot if that's actually the problem.

Tom

1963 Giulia Spider (1750 engine)
1974 GTV
1991 Spider
Former: 1987 Milano Gold
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post #6 of 29 (permalink) Old 07-15-2017, 01:59 PM Thread Starter
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Thanks for the input so far. As long as I have your attention, a few more comments/questions.

1. FPR is Bosch, branny new.

2. will try pinching the return line trick. This could mean an obstruction between the tank and main fuel pump if it works.

3. Should the in-the-tank fuel pump run constantly while the engine is running? From the sounds of it, it is..... Is there a feed back loop (low pressure, start pumping) or simply an "on" state?

Thanks again. BTW, just came in from the garage. She's purring like a well fed cat...........

Anybody have a name for a beautiful, yet psychotic, Italian woman? It's time to christen the Spider.
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post #7 of 29 (permalink) Old 07-15-2017, 02:02 PM Thread Starter
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Quote:
Originally Posted by Gubi View Post
There's a check valve in the main fuel pump. Between that and the fuel pressure regulator, it should hold pressure in the rail with the car off. You may be losing pressure at one or both ends, or have an injector that's leaking with the car off.

You'd need to hook up a fuel pressure gauge and monitor/test to troubleshoot if that's actually the problem.
New main fuel pump. That indicates a leaky injector.
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post #8 of 29 (permalink) Old 07-15-2017, 02:48 PM
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Quote:
Originally Posted by blkzoe View Post
FPR is Bosch, branny new.
New can be faulty. Not likely but don't assume.

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Should the in-the-tank fuel pump run constantly while the engine is running?
Yes, both pumps should be powered on while the engine is running. They are on the same circuit. The early L-jet models (until 84 or 85) came with an inertia shut off switch intended to cut power in the event of an accident. But they were often problematic - would cut power with a bump in the road or even for no reason. It was then determined that the drive relay would function as the safety shut off - if the engine stalled (as in an accident) it would cut power to the fuel pumps so the inertia switch was eliminated. If you car has one you can safely bypass it by connecting the two wires together assuming the drive relay works as intended.

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~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
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Last edited by ghnl; 07-15-2017 at 02:51 PM.
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post #9 of 29 (permalink) Old 07-15-2017, 04:18 PM
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My bet is a faulty cold start injector. I had the same symptoms recently and that's what my problem turned out to be.
Try this: the next time the car is cold (has been sitting overnight or a day or two), unbolt the CSI from the plenum and point the tip in a clear jar or bottle while an assistant turns the ignition key to start. If no fuel sprays into the bottle you either have a faulty Cold Start Injector or Thermo Time Switch. The TTS controls the CSI, and it is normally closed when the engine is cold, so it can be tested with a multimeter set on ohms/resistance between the contacts and engine ground.
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post #10 of 29 (permalink) Old 07-16-2017, 04:26 AM
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Quote:
Originally Posted by Norseman50 View Post
My bet is a faulty cold start injector. I had the same symptoms recently and that's what my problem turned out to be.
Try this: the next time the car is cold (has been sitting overnight or a day or two), unbolt the CSI from the plenum and point the tip in a clear jar or bottle while an assistant turns the ignition key to start. If no fuel sprays into the bottle you either have a faulty Cold Start Injector or Thermo Time Switch. The TTS controls the CSI, and it is normally closed when the engine is cold, so it can be tested with a multimeter set on ohms/resistance between the contacts and engine ground.
Does the CSI fire regardless of temperature?
edit - just checked the L-Jet troubleshooting and see it says under 86F.

Mike

'87 Quadrifoglio

Last edited by mcola; 07-16-2017 at 04:55 AM.
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post #11 of 29 (permalink) Old 07-16-2017, 02:05 PM
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My 86 has the exact same issue. Daily driven, you'd never notice. Let it sit 1.5 days, it sort of 'coughs' to life after cranking a bit longer. After that...crank crank crank......crank. I also have a new fuel pump (bosch) and have tried a new after market pump (no change), new FPR, new CSI from Vick Auto (prob. fiat), New TTS, new ECU temp sensor. All new.

Try this: Let it crank for a short period of time. Walk a way for 5mins. Does it start right up, then? That's what I usually do after its been sitting, to avoid long cranking times.

I've used a fuel pressure gauge, which led me to having the injectors re-built. After that, she ran much better and held good pressure all day, but a hot start issue that was only irritating became really crappy. A new TTS fixed that.

The only sensor that I haven't looked at is the air temp sensor in the AFM. It's not replaceable..but I don't think that could be it.

Let us know what you find!! My Veloce is getting it's engine rebuilt so I can't troubleshoot, but I look forward to getting her back and figuring it out.

86 spider Veloce
74 TR6
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post #12 of 29 (permalink) Old 07-16-2017, 03:51 PM
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Weak or inop in tank pump can cause this.

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 #13 of 29 (permalink) Old 07-16-2017, 04:43 PM
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How long should the CSI release fuel, and should fuel squirt or just dribble out.
I ask because my car has been taking longer to start lately too, so I pulled the CSI to make sure its working.
Seemed like it only dribbled fuel and only for about 1-2 seconds. Normal?

Mike

'87 Quadrifoglio
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post #14 of 29 (permalink) Old 07-16-2017, 05:10 PM
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The CSI should spray like a regular fuel injector. The length of time depends on the temperature (of the engine/coolant). Longer (a few seconds) if very cold, less if not very cold.

- - Eric
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~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
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post #15 of 29 (permalink) Old 07-17-2017, 03:37 AM
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...and after x number of seconds, the bimetallic strip in the TTS, being heated while the starter is engaged, will open the ground circuit for the CSI. The CSI then stops spraying fuel. This is to prevent flooding the engine with excessive cranking.

Jim

Series 2 USA 1750 GTV (in Series 1 European clothing)
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