E30 Zone

Good evening,

As the title says, i end up replacing the fuel pump every 2-3 months ever since i got the car in January 2019.

I first purchased a Bosch unit, the check valve failed (no pressure after switching off, confirmed by sending the injectors out for testing, leak free). Fuel starvation occurs when cold and warm, some hiccuping and so forth.

Replaced it with another Bosch unit, few months later, the same exact problem occured. So i got an aftermarket cheap complete unit (€30 with shipping), and the same thing happened in a few months.

Got a bit more "mid ranged" pump (€50) and yes, the same issue(s) started.

Now, i am in the same boat once more, and i have no idea what would cause a brand new fuel pump (several) to first have a check valve fail, then to cause pressure and delivery issues (starvation).

Both the DME and Fuel pump relays are new-ish. I picked them up from my local dealer last year, to be sure that nothing fails, i replaced every sensor you can think of, except the ICV, AFM and DME (icv got a nice clean, DME never opened and so is the AFM).

I went through the Bentley manual, other than checking for fuse 11, bypassing the relays, checking power at the pump connections (and amps for drainage), i am at a loss on what else to check.

It maybe an electrical issue, very minor that is slowly causes issues down the road with time, but then why would the check valve fail?

I run the tank a lot on near empty, MAYBE it is my fault? and i am allowing the fuel to "slosh away" to the driver's side of the tank, causing the pump to overheat?

Could one or both of the main relais be the cause? causing more power to be transferred to the pump? overvolting it (if that is even a term) thus shortening the lifespan?

I have another new cheap pump arriving tomorrow, not worth spending €80 on a Bosch quality one, till this mystery is solved.

FYI I sent the injectors out again to be double and triple checked, they flow nicely, within specs and so forth, FPR is new and today when i re-installed the injectors, there was no pressure in the rail (after about 1-2 hours of sitting) and the pump is loud when i bypassed the relay to check for leaks.

Maybe that battery fuse link has some rust? or corrosion in one of the relay wires to the box?

Thank you.

PS: I still have the original DME and Fuel Pump relay, i could probably swap them out when i install the new pump? maybe one or more of the internal circuits in the relay power supply is faulty?

Maybe you didn't realise but Bosch parts are one of the most copied parts out there, especially fuel pumps, the fakes are everywhere. In my opinion £80 is not enough for a new quality pump, they are more like £150, I always buy VDO or Siemens

DanThe wrote: ↑

Mon Jan 13, 2020 7:38 pm

Maybe you didn't realise but Bosch parts are one of the most copied parts out there, especially fuel pumps, the fakes are everywhere. In my opinion £80 is not enough for a new quality pump, they are more like £150, I always buy VDO or Siemens

I did spend a lot on a new Bosch TPS sensor that failed within a few weeks. Drove me crazy re-testing every tiny detail in the engine bay, only to find out the new TPS is faulty.

€80 is just the pump, not the complete unit that drops in. You really think it is down to be having rubbish luck with parts?

have you done a fuel pressure check during operation? does the rail pressure drop immediately after switch off? In my experience on an e30 pressure is not going to stay at the rated pressure forever it will slowly drop over time which never seemed to cause issues as the lines were still full of fuel and when crank the pressure would jump up very quickly.

i'm not convinced you have a pump problem as you've not mentioned a delivery problem where the pump is actually dead so there are a bunch of other things that can cause it to run poorly.
if you indeed do have pumps that run but dont deliver properly then id be look at the electrical side of things e.g. a low voltage under load

You don't mention fitting a new fuel filter??

Have you done so and is it the right way round?

Paul

paultv wrote: ↑

Mon Jan 13, 2020 9:25 pm

You don't mention fitting a new fuel filter??

Have you done so and is it the right way round?

Paul

I was thinking exactly the same as regards to the filter. I've know a pump fail due to a completely blocked fuel filter.

Also the O.P mentioned the check valve in pump failing. Can one not simply replace this pump check valve with a one way non return valve somewhere along the main fuel supply line?

Yes, numerous times.

And to be sure, i even installed new fuel filters with the flow arrows facing the engine, and one time with the flow direction arrows facing the tank to see if there was any impact.

Boilie, once the check valve fails, i start to notice hesitation from off to on throttle, which with time, leads to slowly showing less and less fuel pressure when running. I did get an aftermarket check valve and placed it after the pump, but it will only delay the inevitable.

reggid wrote: ↑

Mon Jan 13, 2020 8:58 pm

have you done a fuel pressure check during operation? does the rail pressure drop immediately after switch off? In my experience on an e30 pressure is not going to stay at the rated pressure forever it will slowly drop over time which never seemed to cause issues as the lines were still full of fuel and when crank the pressure would jump up very quickly.

i'm not convinced you have a pump problem as you've not mentioned a delivery problem where the pump is actually dead so there are a bunch of other things that can cause it to run poorly.
if you indeed do have pumps that run but dont deliver properly then id be look at the electrical side of things e.g. a low voltage under load

With new pumps installed, i see around 2.6bar on idle.

Once i start experiencing the "issues", i see less and less fuel pressure both when running and when the engine is off. I recall one time, the fuel pressure dropping right away after shut off.

I found three of the old pumps in my basement and applied 9v to them to check (i do not have 12v source at home), two pumps were just grinding like a blender, clearly indicating the internals were shot. The other pump had a very smooth running operation, i will be installing that today to test it when mounted.

I am willing to double check the electricals as well, especially under load, looks like i have to come up with some wiring solutions.

Sounds like it's time to get some fuel pressure readings done. You should test the full pressure ability of the pump by blocking the return line, this should produce 5 bar easily. At idle you should have 2.5 bar ( 3 bar less the negative manifold pressure ) blocking the vacuum pipe to the FPR should see the pressure rise to 3 bar. Then monitor the fuel pressure in the supply hose and block the return, this tells you if the check valve in the pump is ok, pressure should not drop below 2 bar according to the book. Blocking the return pipe, the supply pipe and the vacuum pipe whilst the system is pressurised and watching the pressure will show you if the injectors are leaking.

And yes I bought a spare cheap pump and it was noisy and ran for a few days, also I agree there are loads of pump makers and they're all made by the same unmarked brand.

A relatively expensive VDO runs quiet and almost forever

Paul

paultv wrote: ↑

Tue Jan 14, 2020 8:25 am

Sounds like it's time to get some fuel pressure readings done. You should test the full pressure ability of the pump by blocking the return line, this should produce 5 bar easily. At idle you should have 2.5 bar ( 3 bar less the negative manifold pressure ) blocking the vacuum pipe to the FPR should see the pressure rise to 3 bar. Then monitor the fuel pressure in the supply hose and block the return, this tells you if the check valve in the pump is ok, pressure should not drop below 2 bar according to the book. Blocking the return pipe, the supply pipe and the vacuum pipe whilst the system is pressurised and watching the pressure will show you if the injectors are leaking.

And yes I bought a spare cheap pump and it was noisy and ran for a few days, also I agree there are loads of pump makers and they're all made by the same unmarked brand.

A relatively expensive VDO runs quiet and almost forever

Paul

I actually did this test, back when i was on the 2nd or maybe 3rd new pump installed. I installed the gauge directly after the pump and blocked the return line. I did indeed see 5 bar, i tested it on the rail and saw the same results. 2.6 bar on idle is what i see with a "good" pump", disconnect the FPR vacuum line and i see a spike maybe 3 bar.

With a failing pump (again either the 2nd or 3rd installed pump), blocking the return line (with the FP gauge mounted on the rail or directly after the pump) and blocking the return line, i see less pressure and once i removed the relay jumper, the pressure dropped (which shows the valve in the pump failing).

Injectors were ruled out everytime, since i removed the whole fuel rail and ran the pump, clamped both return and supply lines and watched for any drop in pressure, none were found. I also sent the injectors to a specialist, i explained my fuel pressure issues, they tested the injectors extensively and sent me video of the spray pattern, resistance tests and leak tests. All 6 injectors are not leaking, fire and spray correctly, so we can 100% rule out injectors.

I am indeed willing to spend the money on quality expensive pump, however the likelihood of 4 pumps failing due to quality is....a bit far fetched. I would like to be absolutely certain, that there is nothing else in the fuel system (electrical or mechanical) that is actually causing these problems. I would rather have €30 pump fail due to an issue with the system and get it fixed, than spend €300+ on a pump and have the same issue arise again.

VDO pump number 228-220-007-001Z is € 326 before shipping (complete unit), VEMO brand V20-09-0412 is €199 both through Autodoc.de.

Which is why i would like to have some advice on what to check electrically or mechanically before spending that much money, being certain that everything is in order and just "cheap parts failing" is the cause instead of an actually issue.

Well everything sounds as its as it should be -

It could well be worth checking the voltage at the pump - not only with a meter but by attaching a bulb between the pump main terminal and earth - does it stay bright when the engine is running ( the pump ) any variation might show a resistive connection in the wiring to the pump - why this would cause a check valve failure I have no idea - but worth a test.

The fuel keeps the pump cool - passing through it, not necessarily by immersion - but maybe if its very low on fuel you're picking up crap that's sticking to the filter and blocking the fuel flow -

just wild guesses!!

Paul

paultv wrote: ↑

Tue Jan 14, 2020 10:24 am

Well everything sounds as its as it should be -

It could well be worth checking the voltage at the pump - not only with a meter but by attaching a bulb between the pump main terminal and earth - does it stay bright when the engine is running ( the pump ) any variation might show a resistive connection in the wiring to the pump - why this would cause a check valve failure I have no idea - but worth a test.

The fuel keeps the pump cool - passing through it, not necessarily by immersion - but maybe if its very low on fuel you're picking up crap that's sticking to the filter and blocking the fuel flow -

just wild guesses!!

Paul

I shall do that, check the voltage at the pump itself.

I really checked the tank very well, no dirt, rust or debris, even in the supply and return lines.

Sounds like a real pain in the arse!!

Paul

paultv wrote: ↑

Tue Jan 14, 2020 11:01 am

Sounds like a real pain in the arse!!

Paul

I was running out of ideas, and kept finding nothing.

Maybe it is just cheap parts indeed, but rather go through the pain now to be sure, than €300+ and really get some hurting going.

These old cars sure are full of surprises.

I tried switching out the current "faulty" pump a working one i found in the basement. Unfortunately, the "spare" one is also faulty, as i bridged the relay, it activated the pump but no fuel was being pumped.

So the "faulty" pump was installed, i then swapped out both the new-ish DME and Fuel pump relays with the original 30-year old ones. There was nothing wrong with them, i replaced them just to be on the safe side.

The car fired up within 2 cranks and idled just fine, it drove fine and everything. 2 hours later, i fired the engine up again, it took just 1 crank and it sprung to life without any hesitation.

It is strange, how it would not pass fuel pressure tests, yet now it appears it does. So either there was a loose connection somewhere (pump connector maybe) or one (or both) of the DME and pump relays are internally faulty somehow?

I need to re-test the fuel system again now, but goodness this is turning out to be one mysterious issue.

As you seem to have tried everything and the tank is clean of any sediment/rust particles it just leaves one possibility. In your first post you mention that you run the fuel tank near empty most of the time probably does not help the pump.

It may very well be due to low quality parts in combination of running low on fuel (just above the reserve which is about 10 liters of fuel) and long sweeping corners (living in Bavaria) maybe the problem here.

New cheap pump arrived, will install it tomorrow morning and fill up the tank. For testing, i shall fill the tank anytime the gauge reads 20 liters (1/4 tank) and realistically there is more in there (E30 fuel gauges are funky that way) and see how it goes the next few months.

Hi there, I'm new here and seem to be having the exact same problem...

To summarize:
I'm on my 2 pump, having issues with pressure car runs low on power
New FPR
New filter
New hoses
And a clean tank
Tested injectors, no leaks and resistance is ok, spray pattern seems good to my eyes.

Did you manage to find out what was the problem with yours??

MACS94 wrote: ↑

Mon Apr 12, 2021 9:02 pm

Hi there, I'm new here and seem to be having the exact same problem...

To summarize:
I'm on my 2 pump, having issues with pressure car runs low on power
New FPR
New filter
New hoses
And a clean tank
Tested injectors, no leaks and resistance is ok, spray pattern seems good to my eyes.

Did you manage to find out what was the problem with yours??

I was either running new pumps on low fuel (on reserve or slightly below reserve fuel) or i was unlucky and some Bosch pumps out there are defective.

According to Walbro, they recommend new pumps to be "broken in" during the first two weeks, meaning never run low on fuel during this time, true or not i basically followed this procedure.

That cheap €30 pump i purchased since then is running strong till this day, i did fill the tank when it reached 1/2 at least 3-5 times before i started to go down to reserve/slightly above reserve.