W111 3.5 fuel pump relay location

[sjefke]

My 3.5 fuel pump does not get power (see my fuel pump dead thread). Next stop is to check whether the relay gets power.

First question: Can anybody confirm (for sure) that the relay is the most left one of the two rectangular relays behind the ECU (on passenger side), below the two cylindrical ones? I see a red wire going from the battery to one, and checking the threads wrt 4.5 fuel pumps, that seems to be the one. There is a larger relay immediately to the right of it, which I assume should be the master relay. Can anybody confirm these? Also, what is the rectangular relay below those two?

There are no posts/threads related to the 3.5 fuel pump relay location. I attached a pic, but if somebody has a nice pic with labels, please post for all us 3.5 coupe/cab owners.

Second question: How do you best get to this relay (without removing the radiator)??? I can feel 2 philips head screws and can probably get them out, but what's the best approach? Hate to crack the wires.

If it is the relay I am thinking off, it looks ancient and could very well be the trouble source.

Thanks,

Bert

[sjefke]

Bump. Back from vacation and ready to get in action. Can anybody answer above questions?

Thanks,

Bert

[sjefke]

OK, I answered my own questions and here are the answers for others for future reference:

1 - I found the relay locations in workshop manual section 07-21b, Figure 07-21/3. I attached the figure with legend for relays for others who may need it. I was initially focused on the wrong relay. Fuel pump relay is bottom one.

2 - Easiest way to get them out is to take the whole mounting bracket/plate out. Remove bracket on top of ECU (two 10 mm bolts). Remove two 10 mm bolts next to oil cooler (you may have to loosen oil cooler-radiator bolts and push it sideways just a bit). There is one 8 mm hex screw in the bracket/plate at the bottom left under the ECU. To get to it, Pull out ECU (carefully). It takes a bit of wiggling but the whole thing comes out and you have easy access to relays. Relays are mounted using philips head screws. Easy to strip. You want to get a good pressure on them. Mine came out relatively easily without stripping.

I attached a picture of the removed relay bracket and ECU.

Bert

[Tony H]

Bert,
I glad you got that figured out. I'm sure it will save someone some time in the future(probably me)
Let us know what the final resolution it.
Unrelated note: I am dissapointed to find an increasing number of parts is NLA fo our cars. Will make kepping it up more difficult in the future.

[werminghausen]

Bert

Thanks so much for your research- really great.
Martin

[JPMOSE]

Tony....I agree with you 100%. A lot of the key parts for D-Jetronic are NLA...I have combed the earth and found almost every electronic part new via MB or Bosch P/N search. I have been stock piling new spares over the past year...and this is money I could certainly use elsewhere ($2,300 so far on spares I may never need!). I also follow E-bay daily as new trigger points, temp sensors, etc. appear from time to time. I have an early 1970 280SE 3.5 Cabrio (Euro) which has a different fuel pump, temp sensor and a few other oddities! The W108/109/111/112 series definately has a lot more NLA parts than the W113!

[Tony H]

I have accumulated a lot of D-jetronic spares also-mostly stuff from the Pick and Pull. I am the last person I thought would say this being a former D-Jetronic purist but I am installing Megasquirt on mine (when I get my project back on track) and keeping all the D-jet stuff to put it original if I ever want or need to. I am also going distributor-less with EDIS. I am going to build a new wiring harness and tuck the original one away so I can keep everything original. For a car that is going to be driven it just seems more practical to have a modern FI system.

[JPMOSE]

How many miles do you drive your 3.5 per year? Between having three convertibles (vampires in the dark garage! lol) and traveling to Europe on business a lot. I am lucky if I put 750 miles on each one per annum!

[Tony H]

For the last several years it has been totally dissasembled in my shop undergoing some restoration work. When I get it done I plan on driving it on the weekends and short trips-probably 100-200mi per month. The work has drug out much longer than I expected but life happens along the way.
Do you know Bert? He lives in Atlanta too.

[JPMOSE]

No...I don't know Bert. Details?

[sjefke]

I live in Morningside/Virginia Highlands area of Atlanta (intown/midtown). Where do you live?

Contrary to you guys I use my 3.5 coupe as a daily driver (and truck). My commute is about 10 miles roundtrip to work, so I still put relatively few miles on it. But it is all city traffic. The 41 years of age (10 in my care) are starting to become evident. Steering play is getting worse and engine is starting to smoke more.

Bert

[JPMOSE]

I live in East Atlanta village. My commute to Lockheed Martin is 46 round trip, driving my 560SEL. Good thing I started tele-commuting 3 days a week in January!