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1979 in tank pump and high pressure pump

 
Old 12-16-2018, 06:15 PM
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Default 1979 in tank pump and high pressure pump




So the 79 obviously has more fuel parts at the back of the car than the later cars. You have the filter and the accumulator in the wheel well- I’m not even sure those are available and I bet the car would run relatively fine without the accumulator.

Then you have the different tank shape and tank strap as the in-tank pump comes out to just the high pressure pump and the cover actually holds the pump studs itself as it is assembled.


That said, I am sure few are buying 1000 dollar in take pumps, and the high pressure pumps are somewhat more robust.

The series of events I have had on the really otherwise well running 79 has been an inability of the pumps to start with the relay in. Once you jump it you are fine, but today it started to not like running and the pump suddenly changed sounds from a stronger lower noise to a higher weaker noise.

I took the cover off and the hose looks partially cracking and collapsed, and while moving around the wires for the in tank it is clearly not actually on, per say.

So so I either killed the main pump through sheer blockage, or it’s fine but can no longer run the car fully (it putters along and will rev with effort) with the partially collapsed hose and dead in tank pump.

Question - will the later output piece for the non-in-tank-pump work for the early tanks?

Also - is the hose not stepped like later? Looks to be same ID from one end to the other.


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Old 12-16-2018, 06:59 PM
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The short hose is different for systems using an in tank pump VS a fuel strainer
based on your observations the inner tank pump has suffered a failure and the supply line is partially plugged this will cause the external pump to run hot due to reduced flow and it could also indicate that the pump has ingested debris

running it backwards could flush it out
always replace the check valve with a new part and use new sealing rings
you should be able to swap out the intank pump with a fuel strainer
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Old 12-16-2018, 07:43 PM
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I know you are behind that keyboard Stan, but why do you always sound like a bot?



Originally Posted by Mrmerlin View Post
The short hose is different for systems using an in tank pump VS a fuel strainer
based on your observations the inner tank pump has suffered a failure and the supply line is partially plugged this will cause the external pump to run hot due to reduced flow and it could also indicate that the pump has ingested debris

running it backwards could flush it out
always replace the check valve with a new part and use new sealing rings
you should be able to swap out the intank pump with a fuel strainer
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Old 12-16-2018, 09:02 PM
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Doesnt the 79 have a different thread in the tank outlet? IIRC the early strainer is NLA, so the early in tank pump might be also? 37mm vs 36mm thread? Many cases of warm starting issues with CIS are blamed on accumulator failure, so I wouldnt plan on leaving it out of the system. Check the amps the pump(s) are pulling - my external pulled 7A when last checked. A collapsed hose would indicate the external is sucking hard but not getting anything. IMHO the in-tank pumps are more trouble than they are worth 99% of the time.My car ran fine without one at 120F and 2000' ASL.
jp 83 Euro AT 57k
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Old 12-16-2018, 10:19 PM
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Thanks JP. I was not planning on changing the Accumulator. The filter is newish and not indicated as a problem. I did NOT know, and will need to research your idea that the In tank pump or the threads on the collar for the 79 are different. That would be sad, as I found one on the shelf and thought I had this cracked.

I can just take apart the in tank pump and put it back in without any of its innards. Sure, straining is important, but to see if its this or the actual high pressure pump...

928s don't like sitting.
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Old 12-16-2018, 10:21 PM
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Also Stan - I don't see a check valve other than the accumulator in this system. They added that in 80 when the changed the pump to match L-jet needs.
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Old 12-16-2018, 10:58 PM
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Up to VINs 92881 01287, 92882 0053, 92882 09527, filter thread is 36mm, NLA; after that its 37mm. With in tank pump hose is 928 356 550 04, without pump, hose ends in 05. Some modern in-tank pumps come with 'sock' filters attached, so maybe you could locate one of those and cable tie it where the old pump was inside the tank. I had a pump jam once, and got the obstruction out by reversing polarity - at the wife's suggestion! Got 5+ years out of it afterwards.
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Old 12-17-2018, 01:36 AM
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Sorry my bad I was reading this from my phone and now looking at my PC screen see your pump is different and doesnt have a check valve that is replaceable like the newer styles do.
Do you have any hot starting issues IE it cranks but wont start?
If so then you would be wise to remove the small screw from the top of the accumulator to see if gas comes out,
if so the part has failed.

If your not having any hot start issues then remove the inner tank pump and flush the outer pump , put it back together see how it runs .
IIRC removing the inner pump guts has been done and the engine has been returned to a running condition on a few machines
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Old 12-17-2018, 01:57 AM
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I suspect that the tall outlet on your pump is a built in check valve, which became a separate part on later pumps - try chasing the Bosch part no and see if it tells you anything useful.
jp 83 Euro S AT 57k
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Old 12-17-2018, 03:42 PM
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Originally Posted by jpitman2 View Post
Up to VINs 92881 01287, 92882 0053, 92882 09527, filter thread is 36mm, NLA; after that its 37mm. With in tank pump hose is 928 356 550 04, without pump, hose ends in 05. Some modern in-tank pumps come with 'sock' filters attached, so maybe you could locate one of those and cable tie it where the old pump was inside the tank. I had a pump jam once, and got the obstruction out by reversing polarity - at the wife's suggestion! Got 5+ years out of it afterwards.
jp 83 Euro S AT 57k
Thanks for the info! I will have to take the in-tank out and hack it up and see. I have 3 of the wrong fuel hose.
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Old 12-18-2018, 11:23 AM
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We have all the parts including the accumulators in stock.
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Old 12-18-2018, 08:54 PM
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Hey Roger. Looks like I need the 928 356 550 04 because it has an intank pump I will not replace but will continue to use its guts as the threads are different per JP above. Additionally, the hatch is popping open when I go over bumps, so need the receiver insert.
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Old 12-18-2018, 08:56 PM
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Old 12-18-2018, 10:19 PM
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Originally Posted by jpitman2 View Post
I suspect that the tall outlet on your pump is a built in check valve, which became a separate part on later pumps - try chasing the Bosch part no and see if it tells you anything useful.
jp 83 Euro S AT 57k
Yes it would be surprising for CIS to have no check valve anywhere in the system.
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Old 12-25-2018, 07:47 PM
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It’s back to running well.

The in tank pump pump was dead but not visibly so.

The outer pump also runs fine now.

In tank pump looks to be replaced sometime recently.

I replaced the in take pump with a filter version. Above it says the threads were different on 79s (or some) but in this case I lucked out and it threaded right in. So I used the later pump supply and bolted it back together. I also took the opportunity to clean out the tank.

This is a good car for 500 dollars. Gotta get it smogged.
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