S500 hard starting issue due to fuel pressure?

[bkmobster]

Hello, recently bought this car and is having a long starting issue with this car. I believe it is a fuel pressure issue. I tested it with the fuel pressure with the following results after changing the Fuel Pressure Regulator with Bosch brand

Position 3 key (pre start position): roughly 10 PSI give or take

Car on: 50 PSI steady

Vacuum hose removed from Fuel Pressure Regulator: 60 PSI

Car off: Rapid drop of fuel pressure to close to zero within seconds

I thought changing the Fuel Pressure regulator would fix it but now I need guidance. Starter was replaced by previous owner.

Also when I replaced the Fuel Pressure regulator, a lot of fuel spilled over when I removed the old one if that is any important information. I saw no visual fuel leak on the top end nor did I smell gas once everything was put back together. Maybe check valves? I do not know if I have a dual or single fuel pump if anyone can help me figure that out I have a 1995 s500 coupe vin# WDB1400701A239971

 

[gsxr]

Hello, recently bought this car and is having a long starting issue with this car. I believe it is a fuel pressure issue. I tested it with the fuel pressure with the following results after changing the Fuel Pressure Regulator with Bosch brand

Position 3 key (pre start position): roughly 10 PSI give or take​

Car on: 50 PSI steady​

Vacuum hose removed from Fuel Pressure Regulator: 60 PSI​

Car off: Rapid drop of fuel pressure to close to zero within seconds​

I thought changing the Fuel Pressure regulator would fix it but now I need guidance. Starter was replaced by previous owner.

Your symptoms indicate a failed fuel pump. Your car has the single pump with integrated pressure check valve.

EPC shows Mercedes part # 000-470-95-94, make sure to only buy OE or OEM Pierburg, not any cheap off-brand pump. OE is about $300 MSRP, OEM Pierburg is around $180 from most vendors. You could also try the Bosch pump (p/n 66150 or 0-986-580-372). Make sure to only buy from a reputable vendor, there are a lot of counterfeit parts on the market these days.

Also when I replaced the Fuel Pressure regulator, a lot of fuel spilled over when I removed the old one if that is any important information. I saw no visual fuel leak on the top end nor did I smell gas once everything was put back together. Maybe check valves? I do not know if I have a dual or single fuel pump if anyone can help me figure that out I have a 1995 s500 coupe vin# WDB1400701A239971

If the fuel tank is closer to full, you may get fuel spilling out with the FPR removed. Best to replace this with the tank near empty.

EPC screenshot below shows that your car is one of the first after the switch to single pump.

 

[bkmobster]

Your symptoms indicate a failed fuel pump. Your car has the single pump with integrated pressure check valve.

EPC shows Mercedes part # 000-470-95-94, make sure to only buy OE or OEM Pierburg, not any cheap off-brand pump. OE is about $300 MSRP, OEM Pierburg is around $180 from most vendors. You could also try the Bosch pump (p/n 66150 or 0-986-580-372). Make sure to only buy from a reputable vendor, there are a lot of counterfeit parts on the market these days.




If the fuel tank is closer to full, you may get fuel spilling out with the FPR removed. Best to replace this with the tank near empty.

EPC screenshot below shows that your car is one of the first after the switch to single pump.


View attachment 227797

thank you so much, I called a dealership and I was told I have "both fuel pumps" and I tried contacting classic mercedes parts and they couldn't 100% confirm with my vin which fuel pump.

From what I am seeing, OEM fuel pump offered by dealership is refurbished with core charge. I read that Pierburg Fuel pumps are not made in china? Also i see some people having issues with this pump within a year or 2 installed.

I am leaning towards Bosch pump 66150, any issues with that? Probably order from Rockauto

 

[gsxr]

thank you so much, I called a dealership and I was told I have "both fuel pumps" and I tried contacting classic mercedes parts and they couldn't 100% confirm with my vin which fuel pump.

Whaa....? Your dealer is wrong. See my screenshot above with your chassis number. Note quantity=1. The dual pumps are a completely different design and NOT interchangeable with the single pump.

From what I am seeing, OEM fuel pump offered by dealership is refurbished with core charge.

Correct, the dealer pump is a refurb with a core charge. This miiiight be old stock still made in Poland. Note that sometimes a "refurb" dealer item may be a brand new part, not actually a refurb.

I read that Pierburg Fuel pumps are not made in china?

They used to be made in Poland, but some recent stock is now made in China/PRC. I installed a new Pierburg pump a couple of years ago and it was PRC.

Also i see some people having issues with this pump within a year or 2 installed.

That is possible. The single pump design seems less robust in general. It's nearly silent, and has the check valve integrated. The old dual pumps are noisy and have an external check valve which can be replaced separately. Unfortunately, as noted above, it's difficult / expensive / impractical to try and convert from single to dual pumps.

Also of note, I bought my Pierburg/PRC pump from FCP... and FCP no longer offers it. I suspect that means they had a high failure rate and no longer want to sell it due to their lifetime warranty policy. Cost them too much money, so they simply stopped selling it.

I am leaning towards Bosch pump 66150, any issues with that? Probably order from Rockauto

I think it's worth a try. If you buy the Bosch, please let us know the COO when you receive it.

 

[bkmobster]

Whaa....? Your dealer is wrong. See my screenshot above with your chassis number. Note quantity=1. The dual pumps are a completely different design and NOT interchangeable with the single pump.




Correct, the dealer pump is a refurb with a core charge. This miiiight be old stock still made in Poland. Note that sometimes a "refurb" dealer item may be a brand new part, not actually a refurb.




They used to be made in Poland, but some recent stock is now made in China/PRC. I installed a new Pierburg pump a couple of years ago and it was PRC.




That is possible. The single pump design seems less robust in general. It's nearly silent, and has the check valve integrated. The old dual pumps are noisy and have an external check valve which can be replaced separately. Unfortunately, as noted above, it's difficult / expensive / impractical to try and convert from single to dual pumps.

Also of note, I bought my Pierburg/PRC pump from FCP... and FCP no longer offers it. I suspect that means they had a high failure rate and no longer want to sell it due to their lifetime warranty policy. Cost them too much money, so they simply stopped selling it.




I think it's worth a try. If you buy the Bosch, please let us know the COO when you receive it.

hey, any chance you can help tell me the part number for oem fuel filter I need? and aftermarket Bosch equivalent? thank you. I will tell u the COO when I recieve the Bosch fuel pump.

 

[gsxr]

Filter is 002-477-27-01. The OEM Mahle/Knecht is around $30, Bosch is suspiciously low priced at $10-$15.

 

[bkmobster]

Filter is 002-477-27-01. The OEM Mahle/Knecht is around $30, Bosch is suspiciously low priced at $10-$15.

View attachment 228272

thank you, I opened the cover today to look at my fuel pump setup. the new fuel pumps look skinnier than my oem one from pictures, you think the bracket will hold the smaller fuel pump? or should I order the new bracket?

A 140 470 04 81 BRACKET

 

[gsxr]

That does look odd. Unfortunately the bracket is NLA. If the new pump is smaller diameter you'll need to add a spacer of some sort to take up extra space. It may fit OK, won't know for sure until you get the new pump in hand and take apart the existing setup.

 

[bkmobster]

That does look odd. Unfortunately the bracket is NLA. If the new pump is smaller diameter you'll need to add a spacer of some sort to take up extra space. It may fit OK, won't know for sure until you get the new pump in hand and take apart the existing setup.

thanks I will just order the following

Bosch pump 66150
OEM fuel filter 002-477-27-01
and a used oem bracket on ebay

il reply back when i find out the COO of the fuel pump

thank you for answering all my questions and helping me out.

 

[bkmobster]

Bosch pump 66150 made in Poland

I called a dealership parts place and their "new reman" part number 000-470-78-94-80 is made in Poland too