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Discussion Starter · #1 ·
My question is about when should there be power to the In-tank fuel pump. The Alfa Owners Manual suggests (I think) that there should be power to the In-tank fuel pump when the key is first turned to the ON position.

I do not get power at the initial ON position but I do get power when cranking. Once the key is returned to the ON position the power stops.

What should be happening??
 

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My question is about when should there be power to the In-tank fuel pump. The Alfa Owners Manual suggests (I think) that there should be power to the In-tank fuel pump when the key is first turned to the ON position.

I do not get power at the initial ON position but I do get power when cranking. Once the key is returned to the ON position the power stops.

What should be happening??
It depends what year car. For the Bosch S3 and S4 cars, the L-Jetronic car pumps get a quick voltage fshot for about a second. THe Motronic cars only get power when cranking and running.
 
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Discussion Starter · #3 ·
It depends what year car. For the Bosch S3 and S4 cars, the L-Jetronic car pumps get a quick voltage fshot for about a second. THe Motronic cars only get power when cranking and running.
I guess I should have stated the year. It an 84 so it has L-Jetronic. I don't seem to be getting the one-second power. Should It have power while the engine is running?
 

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Yes it should or the engine will not run. ;)
With the key in the run position and the engine not running, it will not.
 

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The fuel pumps get power only under two conditions: 1) the engine is running and B) the key is turned to the start position. Your L-jet Spider has a device called a Drive Relay. It is located near the FI computer under the shelf behind the passenger seat. When the engine is running the drive relay gets a tachymetric signal via a sense wire on the coil to 'know' the engine is running. When the key is turned to the start position there is a bypass circuit that bypasses the drive to ensure the fuel pumps operate while cranking. Then once the engine starts the drive relay is expected to take over. When you first turn the key to 'on' that initial flow of electrons to the coil will usually trigger the drive relay to momentarily power up the fuel pumps. But since it is not a tachymetric signal the drive relay does not continue to send power to the fuel pumps.

If you are not getting power to the fuel pumps after the engine starts, check the connections at the coil. I think the sense wire is white (or maybe faded yellow?) and it then goes into a braided mesh cable (like a small cable TV wire) & the braided mesh is grounded. I assume this acts a shield for the sense wire. If the sense wire is securely attached then the drive relay is suspect. Unfortunately it is not a generic relay and a new one is rather expensive. Beware of non-Bosch brand replacements that 'fit'. Some are known to not operate properly. The drive relay also acts as a safety device. In the event of a crash it will cut off power to the fuel pumps if/when the engine stalls. The non-Bosch relays may keep the fuel pumps operating. (KAE is one of the non-Bosch brands.)

Is the engine starting when you turn the key to 'start' then dying when you release the key to 'run'? Or is not starting at all? If the latter, I'd investigate the ignition system first. Remember the drive relay needs to see the tachymetric signal to power up the fuel pumps. No spark = no fuel.

Click on the link in my signature for a web page of info about DIY diagnosis for the L-jet Spider. (you may need to click the down arrow to see the full signature)
 

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I do not get power at the initial ON position but I do get power when cranking. Once the key is returned to the ON position the power stops.
That all sounds OK to me.

Are you asking because of a specific problem (poor starting, running or otherwise), or is it just something you wanted to check up about?

I doubt you can test power at the initial Key On (KO) position without a helper, as the relay only supplies power for a second to prime things....so you'd have to be speedy gonzales to turn on the key and get under the car or in the trunk:)

if you want to test both pumps pull out the big fuel relay (Bosch if original or KAE if aftermarket) under the rear shelf, and jump the socket between pin #30 & #87.....then the pumps should both run continuously
 

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Discussion Starter · #7 ·
That all sounds OK to me.

Are you asking because of a specific problem (poor starting, running or otherwise), or is it just something you wanted to check up about?

I doubt you can test power at the initial Key On (KO) position without a helper, as the relay only supplies power for a second to prime things....so you'd have to be speedy gonzales to turn on the key and get under the car or in the trunk:)

if you want to test both pumps pull out the big fuel relay (Bosch if original or KAE if aftermarket) under the rear shelf, and jump the socket between pin #30 & #87.....then the pumps should both run continuously
That all sounds OK to me.

Are you asking because of a specific problem (poor starting, running or otherwise), or is it just something you wanted to check up about?

I doubt you can test power at the initial Key On (KO) position without a helper, as the relay only supplies power for a second to prime things....so you'd have to be speedy gonzales to turn on the key and get under the car or in the trunk:)

if you want to test both pumps pull out the big fuel relay (Bosch if original or KAE if aftermarket) under the rear shelf, and jump the socket between pin #30 & #87.....then the pumps should both run continuously
Thanks Eric and Dom for the complete picture of how the fuel pumps are powered and what to look for. I'll spend some more time digging into what is really going on.

The longer story is that I just reinstalled the engine and trans in the course of a ground-up restoration. The engine started but ran very poorly and would stall. I first suspected a vacuum leak and expected to find a hose not connected. Not the case. All electrical connections seem to be in there correct place and secure. Tested the spark and that seemed OK so I turned my attention to the fuel supply. And that's where I sit. I'll look more closely tomorrow. Thanks
 

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Thanks Eric and Dom for the complete picture of how the fuel pumps are powered and what to look for. I'll spend some more time digging into what is really going on.

The longer story is that I just reinstalled the engine and trans in the course of a ground-up restoration. The engine started but ran very poorly and would stall. I first suspected a vacuum leak and expected to find a hose not connected. Not the case. All electrical connections seem to be in there correct place and secure. Tested the spark and that seemed OK so I turned my attention to the fuel supply. And that's where I sit. I'll look more closely tomorrow. Thanks
Well, if you want to eliminate or verify the pumps as your stalling and poor running cause, you can run a jumper wire from your battery to the middle of the 3 wires on the sender(purple I believe) and that will make the pumps run continuously.

Don't forget to take it off when done! ;)
Greg
 
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That will check the in tank but not the main
Jumping the relay checks both
I think you will find that it runs both assuming you leave the original wire connected to the sending unit still connected.
Make a "Y" splitter at the sending unit to do that.
Maybe I should have said that part.
 

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The fuel pumps get power only under two conditions: 1) the engine is running and B) the key is turned to the start position. Your L-jet Spider has a device called a Drive Relay. It is located near the FI computer under the shelf behind the passenger seat. When the engine is running the drive relay gets a tachymetric signal via a sense wire on the coil to 'know' the engine is running. When the key is turned to the start position there is a bypass circuit that bypasses the drive to ensure the fuel pumps operate while cranking. Then once the engine starts the drive relay is expected to take over. When you first turn the key to 'on' that initial flow of electrons to the coil will usually trigger the drive relay to momentarily power up the fuel pumps. But since it is not a tachymetric signal the drive relay does not continue to send power to the fuel pumps.

If you are not getting power to the fuel pumps after the engine starts, check the connections at the coil. I think the sense wire is white (or maybe faded yellow?) and it then goes into a braided mesh cable (like a small cable TV wire) & the braided mesh is grounded. I assume this acts a shield for the sense wire. If the sense wire is securely attached then the drive relay is suspect. Unfortunately it is not a generic relay and a new one is rather expensive. Beware of non-Bosch brand replacements that 'fit'. Some are known to not operate properly. The drive relay also acts as a safety device. In the event of a crash it will cut off power to the fuel pumps if/when the engine stalls. The non-Bosch relays may keep the fuel pumps operating. (KAE is one of the non-Bosch brands.)

Is the engine starting when you turn the key to 'start' then dying when you release the key to 'run'? Or is not starting at all? If the latter, I'd investigate the ignition system first. Remember the drive relay needs to see the tachymetric signal to power up the fuel pumps. No spark = no fuel.

Click on the link in my signature for a web page of info about DIY diagnosis for the L-jet Spider. (you may need to click the down arrow to see the full signature)
Great information! My '83 has been at my mechanic's shop with a no-start problem (spark, but no fuel). He's been stumped, because the car runs on starter fluid only. He works on all types of cars, so he's not an Alfa expert. He knows about the Bosch L-Jet system and he did mention the fuel pump relay, but he hasn't got around to working on it. I think he'll be happy to find this out.

Thanks for the info!
 
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