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  1. #1
    Veteran Member Four Rings Club Cheetah's Avatar
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    Oct 28 2009
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    49924
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    03 allroad
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    CO

    Engine swap, now no fuel pressure

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    Hi guys,

    I did an engine swap over the last couple months, went from a bad BEL to an APB with about 50k less miles on it. I got the motor in and everything is looking real nice, minus the fact that I have zero fuel pressure. I checked the fuses, and have no power at the fuel pump.

    I did a search and came up with many options, including a bad relay, or any number of bad sensors elsewhere in the car. Would a bad CPS, speed sensor, or other sensor issue cause the pump to not even get power? Funny how I can do the full engine swap and have almost no issues, but when it comes to these nagging little issues I hit a mental wall.

    Where would be my best place to start? I'm going to jump the relay tomorrow and see if it's as simple as that, and I'm really hoping it's not another larger issue, or this rabbit hole of other sensors.

    Mike

  2. #2
    Senior Member Three Rings Wide-66's Avatar
    Join Date
    Jun 17 2011
    AZ Member #
    77041
    My Garage
    1966 Porsche 911 w/ 996 swap, 12 A7, 05 Allroad 6MT, 01 B5 S4 F21, 86 Coupe GT....many more
    Location
    NH

    Quote Originally Posted by Club Cheetah View Post
    Hi guys,

    I did an engine swap over the last couple months, went from a bad BEL to an APB with about 50k less miles on it. I got the motor in and everything is looking real nice, minus the fact that I have zero fuel pressure. I checked the fuses, and have no power at the fuel pump.

    I did a search and came up with many options, including a bad relay, or any number of bad sensors elsewhere in the car. Would a bad CPS, speed sensor, or other sensor issue cause the pump to not even get power? Funny how I can do the full engine swap and have almost no issues, but when it comes to these nagging little issues I hit a mental wall.

    Where would be my best place to start? I'm going to jump the relay tomorrow and see if it's as simple as that, and I'm really hoping it's not another larger issue, or this rabbit hole of other sensors.

    Mike
    CPS triggers FPRelay. I would check there if the pump runs when manually powered.

  3. #3
    Veteran Member Four Rings Club Cheetah's Avatar
    Join Date
    Oct 28 2009
    AZ Member #
    49924
    My Garage
    03 allroad
    Location
    CO

    Little update, bypassed the FPrelay, pump did it's thing and I suddenly found about half the injector seals leaking fuel. I have my previous intake manifold which I'm swapping out now, but this is weird. Would this leak prevent the pump from pumping?

  4. #4
    Veteran Member Four Rings PaperToast's Avatar
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    Apr 29 2009
    AZ Member #
    41811
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    Quadzilla
    Location
    Longmont, CO

    sounds like you have a bad relay, replace and report back
    Rockin' the Rockies
    '01 allroad, 240k woot woot, still boosting on original turbos and tippy, slightly more modified. . .

    Scotty@Advanced, "Push it off a cliff, when it hits the ground you should have a few thousand horsepower available for a brief second."

  5. #5
    Senior Member Three Rings Wide-66's Avatar
    Join Date
    Jun 17 2011
    AZ Member #
    77041
    My Garage
    1966 Porsche 911 w/ 996 swap, 12 A7, 05 Allroad 6MT, 01 B5 S4 F21, 86 Coupe GT....many more
    Location
    NH

    Quote Originally Posted by Club Cheetah View Post
    Little update, bypassed the FPrelay, pump did it's thing and I suddenly found about half the injector seals leaking fuel. I have my previous intake manifold which I'm swapping out now, but this is weird. Would this leak prevent the pump from pumping?
    Check the CPS plug at the firewall if good replace CPS

  6. #6
    Veteran Member Four Rings AudiA4_20T's Avatar
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    Oct 29 2005
    AZ Member #
    8553
    My Garage
    10speed
    Location
    San Francisco, CA

    Did you retain the BEL ECU & Harness?
    - Clint

    Current: 05 B5.5 Passat 4motion 1.8T - Jfonz Tune, 034 HFC, Samco TIP waiting to go on: GTRS, 034 FMIC, 630cc Injectors, Bilstein / H&R Suspension
    Totaled: 04 DG B6 Cabby 1.8T - stock forever
    Gone: White '04 S4 2.7T - Stage 2+
    Gone : Fastest B6 A4 ever - 464awhp/12.1@116
    Gone : 05 DG B7 2.0TQ - Stage 1

  7. #7
    Senior Member Three Rings Wide-66's Avatar
    Join Date
    Jun 17 2011
    AZ Member #
    77041
    My Garage
    1966 Porsche 911 w/ 996 swap, 12 A7, 05 Allroad 6MT, 01 B5 S4 F21, 86 Coupe GT....many more
    Location
    NH

    Quote Originally Posted by AudiA4_20T View Post
    Did you retain the BEL ECU & Harness?
    You are right that is the first question to ask i was assuming long block swap.

  8. #8
    Veteran Member Four Rings AudiA4_20T's Avatar
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    Oct 29 2005
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    Quote Originally Posted by Wide-66 View Post
    You are right that is the first question to ask i was assuming long block swap.
    Yep. Assuming the BEL was retained, next idea is crank position sensor. OP, can you log RPM with vag-com when turning over?
    - Clint

    Current: 05 B5.5 Passat 4motion 1.8T - Jfonz Tune, 034 HFC, Samco TIP waiting to go on: GTRS, 034 FMIC, 630cc Injectors, Bilstein / H&R Suspension
    Totaled: 04 DG B6 Cabby 1.8T - stock forever
    Gone: White '04 S4 2.7T - Stage 2+
    Gone : Fastest B6 A4 ever - 464awhp/12.1@116
    Gone : 05 DG B7 2.0TQ - Stage 1

  9. #9
    Veteran Member Four Rings Club Cheetah's Avatar
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    Oct 28 2009
    AZ Member #
    49924
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    03 allroad
    Location
    CO

    I'm having a friend over this weekend with his VAG com and will do some more research.

    I did keep the ECU and harness from the BEL, swapped the required parts and plugs. I can confirm the fuel pump is good with the bypass, swapped the intake manifolds and I'm getting pressure with no leaks now. I'm having zero firing as well, would this be normal since the relay might be the culprit or the CPS?

    CPS plug is good, engine is turning over nice and smooth, but no firing.

  10. #10
    Active Member Two Rings Middleton7's Avatar
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    Jul 30 2017
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    403965
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    Grand Ridge, Florida

    Quote Originally Posted by Club Cheetah View Post
    I'm having a friend over this weekend with his VAG com and will do some more research.

    I did keep the ECU and harness from the BEL, swapped the required parts and plugs. I can confirm the fuel pump is good with the bypass, swapped the intake manifolds and I'm getting pressure with no leaks now. I'm having zero firing as well, would this be normal since the relay might be the culprit or the CPS?

    CPS plug is good, engine is turning over nice and smooth, but no firing.
    I know this is a long shot, but does anyone you know have a lab-scope? Basically an oscilloscope designed for automotive electronics troubleshooting..

    Sent from my SM-N900V using Audizine mobile app

  11. #11
    Veteran Member Four Rings Club Cheetah's Avatar
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    Oct 28 2009
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    03 allroad
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    CO

    Nope, at least not off the top of my head. What/how would this be used?

    I'll pick up a new relay tomorrow, it's at least easily returnable if that's not the problem.


    Question: If the CPS is bad, or even the FPRelay, would either of those prevent the car engine from firing? I bypassed the relay, and have fuel pressure, could it be that I also don't have spark?

  12. #12
    Active Member Two Rings Middleton7's Avatar
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    Jul 30 2017
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    Grand Ridge, Florida

    You can quickly and easily attach to the signal wire from the CPS and see if it's working, working but reluctor has broken or chipped teeth, working but too low of a voltage.

    Sent from my SM-N900V using Audizine mobile app

  13. #13
    Veteran Member Four Rings Club Cheetah's Avatar
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    Oct 28 2009
    AZ Member #
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    03 allroad
    Location
    CO

    Little update, I put a new FPRelay in, nothing. I also have a CEL and the ESP light on. I'm hoping to have the vag thrown on it relatively soon so I can dig a little deeper into what the ECU is finding.

    I'm also wondering if I have no spark. Actually, I'm pretty sure I have no spark, as I had some fuel sent through to the manifold, but absolutely no firing happened.

  14. #14
    Veteran Member Four Rings Club Cheetah's Avatar
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    Oct 28 2009
    AZ Member #
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    03 allroad
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    CO

    Yet another update, the CPS connector wasn't plugged all the way together. Plugged it in all the way and the car fired right up.

    So, I'm thinking about starting a thread about all the stupid shit we all tend to do tat has caused these little panic filled moments, caused and fixed by missing the little things.

  15. #15
    Senior Member Three Rings Wide-66's Avatar
    Join Date
    Jun 17 2011
    AZ Member #
    77041
    My Garage
    1966 Porsche 911 w/ 996 swap, 12 A7, 05 Allroad 6MT, 01 B5 S4 F21, 86 Coupe GT....many more
    Location
    NH

    Quote Originally Posted by Club Cheetah View Post
    Yet another update, the CPS connector wasn't plugged all the way together. Plugged it in all the way and the car fired right up.

    So, I'm thinking about starting a thread about all the stupid shit we all tend to do tat has caused these little panic filled moments, caused and fixed by missing the little things.
    It is also a good example of listening to advice from members trying to help as the solution was in post #4 however it was overlooked. Glad it was a simple fix and you are up and running.

  16. #16
    Established Member Two Rings Grainreaper's Avatar
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    Nov 19 2016
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    Lake in the Hills, Illinois

    I refer to this sort of thing as an IFS light, it happens all too often as a mechanic, doing a head gasket job, or shortblock replacement, you get pulled off it a dozen times to do other things, when you fire if up you see the check engine light pop on, I refer to that as the IFS light, the "l forgot something" light.



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