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My new walbro in-tank pump is not generating any pressure at…

Customer Question
My new walbro in-tank...

My new walbro in-tank pump is not generating any pressure at the fuel rail, it was a straight swap, the same as the original, which ran for 3 years until it began making loud noises.

Mechanic's Assistant: I'll do all I can to help. How long have you been dealing with this?

3 days...check everything i can think of. no wiring was changed, no plumbing was changed

Mechanic's Assistant: Do you plan on doing the work yourself?

Absolutely, i installed the aftermarket tank myself 3 years ago and rebuilt the whole car. 1969 MGB roadster with GM 3.4L V6 and T5 transmission.

Mechanic's Assistant: Anything else we should know to help you best?

When I turn on the ignition, i hear the pump what sounds like pressurizing the system for about 4 secs just like the old pump used to.

Submitted: 2 months ago.Category: Classic Car
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Answered in 8 hours by:
5/31/2018
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago
Gary
Gary, ASE Certified Technician
Category: Classic Car
Satisfied Customers: 1,985
Experience: Senior Technician
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Hello! My name is Gary.
Welcome to JustAnswer.
I'm reviewing your question now, and will post back with a reply shortly.

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Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

Sounds like you know your car well enough.

The only way I could see these happening is the pump is wired backwards.

Can you double check polarity at the pump?

Gary

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Customer reply replied 2 months ago
I was in contact with the custom tank manufacturer late yesterday. He suggested the same thing, i will check this morning. The only way this could happen is if Welbro changed the polarity configuration over the last 3 years. It's exactly the same model pump as the original, I didn't disturb the in-tank wiring or snap-in connector (which only fits one way) nor did i disturb the outside tank wiring...one of life's little mysteries
Customer reply replied 2 months ago
OK I reversed the pump connects to no avail, while underneath i checked the wiring to the tank and the original connections were correct so i switched them back again. I have OBD1 Scanner software on my laptop and i ran a scan when I cranked the engine. The 24X sensor value was 3188. The 3X Time Period was 999.98, not sure what that means but it was at zero before I cranked. I know that on this engine the 3X crankshaft sensor has to read a value or the ignition control module won't send a spark. Interestingly enough the same software reported a zero for fuel pump voltage which makes not sense since you can hear the pump start up and run for few seconds when you turn on the ignition. Does any of this make sense to you becasue I'm pretty well out of ideas. I've attached two screen shots because i had to pan down to the lower half to get all the readings.
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

Does that 24X value change from 0 to other values ?

3188 doesn't make sense.

Intake air temp at -31 is wrong.

Spark advance at 14851?

A lot of look correct, but some things are ambiguous.

And your car was running before you swapped the pump, correct?

Gary

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Customer reply replied 2 months ago
the car was running. it two problems that i needed to address, the first was that the aftermarket headers were quite close to the 3X crankshaft rotational sensor. The car would start fine when cold and even after a few short trips, however once the sensor got hot it would malfunction preventing the car from starting since the ECM initially relies on a signal from the 3X sensor to start. The solution was to wait 15 minutes and away she would go. Just a few days ago the in-tank pump began to get noisy, after 3 years of running it was generally thought that Ethanol in the gas had eventually taken its toll, hence the replacement pump.
I have a cold air intake on the car which I have removed during troubleshooting so the intake air temp sensor is hanging down which might be the reason for the strange value. When was the car was running all of the retrieved data was normal. Its my understanding that even the absence of a spark would not prevent the fuel system from initially pressurizing the system. its a pretty basic fuel delivery system. i have to get the car even higher so i can inspect the steel fuel lines just at the point where they turn at 90 degrees to run under the car.
there is a slim possibility that they might have been crushed by a trolley jack thereby seriously restricting flow.
Customer reply replied 2 months ago
Maybe the original pump became noisy as it was trying to overcome a restriction in the line to the fuel rail
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

Ok, certainly sounds feasible.

I would run the pump with the fuel pump relay bridged, then see what you get at the rail.

Gary

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Customer reply replied 2 months ago
Gary,
That makes perfect sense. I was planning to disconnect the short length of flexible hose at the fuel rail and run a length of hose from the end of the steel tube down into a bucket just to see if i have fuel delivery right up to the rail. If not I will slowly work backwards towards the tank. If I have fuel up to that point i can reconnect to the rail, since i have a fuel pressure gage installed on the rail bleed port and the gage is fitted with a bypass bleed button and a long length of clear hose i can activate that to drive any air out while the pump is operating.
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

Ok, I'll leave with you for now.

Gary

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Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

Hello again,

I hope my advice has been of assistance to you.

Kind regards.

Gary

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Customer reply replied 2 months ago
Gary
It turns out that the gage I had connected to the fuel rail was faulty and therefore the pressure relief function on it was also faulty. The pump was developing pressure all the time. After I got the problem with 3X sensor fixed the car started straight away. Unfortunately the car still doesn’t start when hot, wAit 15 mins and it will start. Been troubleshooting this for months. It’s not heat soak. Everyone thought it was the 3X sensor connector going open circuit when hot but now it’s covered in heat shrink and has a aluminum heat shield beween it and the header
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

What codes does it set now?

Sounds like a heat affected crank sensor failure to me.

Gary

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Customer reply replied 2 months ago
I'll have to see if i can duplicate it tomorrow, I was picking up a take out for the family dinner tonight, i had to sit there until the electric fan turned off then I could start the car again and get home. The fan is being activated by a simple temperature switch in the top of the radiator instead of the signal from the ECM (long story). It doesn't always work out that way, I've had the car fail to start many times without the fan running. Are you referring to the 3X crankshaft sensor which is the one I have just replaced and added protection to or are you referring to the 24X Crankshaft sensor behind the crankshaft pulley? If its the 3X sensor I don't know what else I can do to protect it further
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

I would say the 24X.

When it won't start, trickle some water over it.

Gary

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Customer reply replied 2 months ago
Gary,
I had previously understood that a working 3X sensor is necessary for the engine to start and that it is only utilized at low rpm ( I believe up to 900rpm) then the 24X takes over as it has greater resolution. I don't think the absence of a 24X sensor signal prevents the engine from actually firing.
Customer reply replied 2 months ago
Here's what I just read:
The engine should start with a faulty cam position sensor (DTC 17), or a faulty 24X crank position signal (DTC 36). But the 3X crank position failure prevents the engine from starting. That would be a case where there is no spark present, and code DTC 82 would set.
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

Yes, that is all correct.

So you need to be chasing a 3X type fault.

What codes do you get?

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Customer reply replied 2 months ago
Gary, I hopefully be able to let you know tomorrow. Another test would be to measure the resistance across its connections. It should be between 900 and 120 ohms. If it measures as an open circuit or a direct short when hot then we can confirm the problem although I don't know how to avoid it short of pumping cool air across it. The resistance can be measured at the two pin connector on the ignition control board
Customer reply replied 2 months ago
Heres what I have already done to try and alleviate the heating up of the 3X sensor. I have added additional insulation on the connector wiring, added an sheet aluminum heat shield between it and the header down pipe and finally I hammer peened a dent in the header pipe to open up the air gap between it and the sensor. For the record, there are at least 30 other people in the US that have done exactly the same engine conversion on an MGB and used the same custom headers and none of them have experienced the same starting issues.
Customer reply replied 2 months ago
Sorry, but I keep thinking of things to add. I have heard that on this L32 engine that the position of the ignition control board and its three coils located where it is on top of the motor is prone to cause premature heat failure of those components. Out of an abundance of caution I have replace two of the boards in the last three years and if I remember right three sets of coils when their plastic cases developed cracks. Since the signal from the 3X sensor is fed to the board via the two pin upper connector and then relayed out to the ECM via one of the two lower connectors, it could still be a fault on the board also.
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

Yes, it could be a DFI module board, or it could be a poor connection at the board connectors.

Gary

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Customer reply replied 2 months ago
Hi Gary,
will have have to pt the trouble-shooting on hold for a week while I'm on a business trip to Germany. Been doing a bit more reading on various online Camaro sites. There a number of people there experiencing similar symptoms. Tow things came up as things that solved a few people's problems. The need to wrap the starter with insulation when using headers and adding an extra ground cable between block and frame. Not too convinced that it will help me but I'm prepared to try anything at this stage. I have the insulation, a ground cable and a new DFI module board on order so they will be here when I get home.
Classic Car Mechanic: Gary, ASE Certified Technician replied 2 months ago

That's ok.

If the question closes, and you wish to continue with me, you can make a request for me.

Have a happy and safe trip.

Gary

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