What happened? -- S70 T5 140K

mar601 · Post by **mar601** » 15 Apr 2016, 11:52

It was the fuel pump relay everybody -- thanks scot850 -- nail on the head. so jumped it for now but replaced those 2 caps in the relay as well but I'll test that out later. i've been in electronics all my life and there is some crazy stuff going on in front of that relay coil -- a big pin chip, 3 or 4 diodes some smd components, weird. have no idea what they're doing -- a relay is either on or off for christs sake. i'll have to look at the schematic. anyone know?

Post by **abscate** » 15 Apr 2016, 11:58

I think it isn't just a relay but carries some of the logic for fuel pump on/off.

The fuel pump relay on ME7 cars seems a little more reliable based on anecdata here. I'm still on my original.

Post by **scot850** » 15 Apr 2016, 13:51

Glad to be a help!

Hopefully that is all it was and with a new or good used part, it will hopefully be back to it's best.

Neil.

Post by **rguzz** » 15 Apr 2016, 21:22

Polksmafia's link provides some pump options. Replace the 20+ year old pump or risk getting stranded someplace unpleasant. Cost is not prohibitive, and if the relay fixed things for now, you can replace the pump relatively electively. Piece of mind doesn't come at an exorbitant price with this repair why risk not doing it. FP failure is just too high on the what can leave me stranded list to ignore.

Post by **rspi** » 16 Apr 2016, 04:08

As far as I know my fuel pump has 310,000 miles on it.

Odd for a relay to give you more power than ever.

Post by **rguzz** » 16 Apr 2016, 09:06

Ha! "Fuel Roulette" Robert.

gswede · Post by **gswede** » 17 Apr 2016, 06:14

I dont believe this to be the relay either. I`d suspect vacuum hoses, check they are all connected. It is not uncommon for vaclines to develop pin holes in them, say if the hose to WG is bad, WG will not function as intented. The same could of course happen to the red hose going from pressure port on turbo, same behavior, if leaking or popped off/cracked at turboport, not enough pressure to open WG as intended. Beware your rods.

Also check the PCV hoses, the hard plastic pipe going to PTC valve has a nasty tendency to break clean off 5-8inches from the ptc, inside the mush foam protecting the hose and vacline. Suspect your car is running lean or not enough pressure to operate WG thus increasing power.

Sommerfeldt · Post by **Sommerfeldt** » 17 Apr 2016, 06:31

gswede wrote:I dont believe this to be the relay either.

Well... he kinda already figured out that it was, in fact, the relay...

- S

gswede · Post by **gswede** » 17 Apr 2016, 06:49

Have you tried bridging your relay ports, No?
Well I can tell you it will not make the car go faster making the pump work at 100%. I cannot understand how a faulty relay would make the car behave as described, if faulty not engaging, car will not run, if faulty in engaged position car will run but not add power in any way.
Actually it will make car stumble under acc due to excessive pressure coming on to early.

mar601 · Post by **mar601** » 17 Apr 2016, 06:52

yes and just going to buy a new one -- replaced both caps which is a waste of time -- they tested good but still could be leaky so went ahead and did it. wouldn't recommend anyone screwing with this relay FYI. I have repaired other ones with simple dirty contacts etc.

for now, it's a paper clip.

What happened? -- S70 T5 140K

Re: What happened? -- S70 T5 140K