New Fuel Relay-not working (wire bridge 87/30 works fine)

[iamdetailing]

Hello guys
I’m new owner of 92 500E which was always my dream.

I was very lucky and find good car for good price but since that the car was sitting last 7years I already did many things, from coeaning gas tank, changing some parts to super deep cleaning everything on that car…
Will be really good video about it on youtube.

But one thing making me headache

So I start changing both fuel pumps, filter, oils, spark plugs, cleaning tha gas tank, before first start… when I was ready and excited nothing happened and I find out that I don’t have a power on fuel pumps which is usually fuel relay.. so just to be sure I pluged wire on pins 87 and 30 and everything worked great.

So I bought new relay and the car started and runs but not perfectly smooth and when I drove it I heard and felt that something is wrong like misfiring or something… it wasn’t smooth and not much power from engine.

So I removed that new relay and put there wire again and cars runs smooth and with all power that should be there. So I returned the relay and buy another one… but still same problem.

So there must be something that control this fuel (multipurpose) relay and that creating problem because injectors not getting as much fuel as they need… with new relay I have very low pressure on fuel injectors, but with wire “bridge” 87 and 30 it’s high pressure and runs perfect.

So I need diagram to find what control that relay or if anyone can point me right direction what I should check or change

Very appreciate any response

 

[gsxr]

When the engine is idling, remove the rear seat and see if the relay is clicking. If so, your LH module is defective and needs repair or replacement. The LH module is what powers the relay. The relay itself almost never fails, but the clicking problem is pretty common, and can cause running issues due to fuel pressure fluctuations.

Congrats on the purchase, and welcome to the forum!

 

[iamdetailing]

Thank you

I tried and relay not clicking... something else I should try?
Which one is LH module?

 

[gerryvz]

Thank you

I tried and relay not clicking... something else I should try?
Which one is LH module?

The one that says "LH 0008" at the bottom of the photo.

 

[iamdetailing]

Oh I see

So should I just buy this LH module on eBay and switch it?

Definitely the relay not making any clicking and it's brand new... And I tried again just connect two pins 87 - 30 with wire and runs beautifully, but basically immediately when I switch that wire for relay the engine starts shaking and I'm losing fuel pressure on fuel injectors.

 

[gsxr]

Definitely the relay not making any clicking and it's brand new... And I tried again just connect two pins 87 - 30 with wire and runs beautifully, but basically immediately when I switch that wire for relay the engine starts shaking and I'm losing fuel pressure on fuel injectors.

This doesn't make sense. If the relay isn't clicking, but bypassing the relay cures the problem, something really bizarre is going on.

 

[iamdetailing]

I pushed and hold that button next to control modules for 3 seconds…. After that light 6 times blink… does it help that information?

 

[gsxr]

I pushed and hold that button next to control modules for 3 seconds…. After that light 6 times blink… does it help that information?

That appears to indicate fault code "Idle speed control inoperative", which should trigger the Check Engine light on the dash. This is only showing faults from the CARB / diagnostic module. There are separate faults from the other 5 powertrain modules but you need a hand-held blink code reader, or Star/SDS digital scanner.

Read the "De-Coding" subforum for details on how to check & clear all codes.

 

[iamdetailing]

I’ll do that
Thank you for your help

 

[Jlaa]

Also,
before you buy a new module, open up the existing LH module. How do the capacitors look? Do they look like they are bulging?
Is a a very common issue. You can do a search.

Fuel pump/relay and multiple other problems after 4 years in storage and 7 without use | M119 Engine

I need some advice. I have a 93 500E and I replaced the fuel pumps, filter, and the relay (used relay) back in June because the car wasn't starting after being stored for 4 years. I solved the fuel problem and since then, I've been restoring the car. Today when I tried to start the car after...

www.500eboard.co

Anyone rebuilding LH modules? | Electrical, CAN and Wiring

Hi all, Just used my last working LH module to cure my chattering fuel pump relay and would like to have the failed unit re-capped (assume the problems are due to old capacitors) as a backup/spare. Is there anyone providing this service. My LH is from my 1992 500E. Thanks in advance! Joe

www.500eboard.co

 

[iamdetailing]

It looks normal insinde

 

[Jlaa]

It looks normal insinde

Really? Some of those look faintly bulgy to me or just starting to have brown stuff on top. I can't really tell.

 

[gsxr]

You can try a different LH module for testing (any M119 V8 module will work, doesn't matter what part number). If the spare cures the problem, that confirms your existing LH needs repair. Most likely it's the capacitors.

How old are the fuel pumps, btw?

 

[iamdetailing]

Ok I will buy spare LH module and hopefully it will work.
Fuel pumps are brand new.

 

[gsxr]

Ok I will buy spare LH module and hopefully it will work.
Fuel pumps are brand new.

Note that for TESTING, any M119 LH will work.

But for a long-term replacement, it needs to be a 5.0L module... and to not lose WOT enrichment function you want a 1992 5.0L module ($$$).

 

[iamdetailing]

I have also 1992 SL500 but I think in that car the engine looks a little different… looks like there is mechanical fuel injection

 

[gsxr]

I have also 1992 SL500 but I think in that car the engine looks a little different… looks like there is mechanical fuel injection

1992 500SL has M119.960 with CIS-E injection... completely different injection system. Can't use anything from that engine on the 500E. Even the block and manifolds are different.

 

[iamdetailing]

Good to know Thank you for info…
I will just buy that part and we’ll see.