# Fuel Pump Relay (5-pin) Diagnostic Needed



## axe_ace (Jun 21, 2011)

The diagnostic "flow chart" I'm using for my no-start / no fuel pressure has taken me to :

TESTING


Operating Test
Have an assistant operate the starter. Listen near the fuel pump location to determine if the pump is running.
If the pump is not running, check the wiring and the fuse on the front of the fuel pump relay.
If the fuse is good, replace the fuel pump relay.
If the fuel pump still does not operate, and you're sure there are no loose connections in the wiring, the fuel pump is faulty and must be replaced.


-I'm nearly ready to replace the relay, per instructions, however before I shell out the money for a new relay (I can bypass the relay with a paper clip and operate the vehicle) I would like to determine if the relay is is getting whatever signal actuates the relay itself. -Presumably the relay incorporates the timer and other logic circuits which may well be the root of the problem, but if someone could provide me with a pin-out on the socket the relay goes into I'd feel better about committing to the purchase of a somewhat expensive- and non-returnable- electronic component (I say electronic rather than electrical due to the presence of an integrated circuit in the relay)

It may very well be the best practical way of testing to "throw parts at it" until it's fixed, but hopefully someone here has encountered this (maybe more than once) and can guide me with some probability down the right path,

Thank you,

Ace


----------



## cuppie (May 4, 2005)

The pinout, friend, is printed on the relay (or, should be, if you still have an OE relay in there.)  

And, the troubleshooting instructions are missing a step - the first step:
Turn key on. Pump run yes/no? 
If YES, then you know that the pump wiring, as well as relay ground and power supplies are OK (but, not if the tach signal to it is OK.)


It's actually rather simple how it works - it's just a standard 4-pin 'Bosch-type' relay, plus a little logic controller, with an extra pin (which leads to coil terminal 1 (negative) as an input to the logic in it.)
Because of that, there are a couple of other things you can do as checks:
- pull your horn relay (marked with "53"), install in place of fuel pump relay. Turn key ON. If pump runs continuously: main power, key-on power, line to pump, and relay ground are all ok.
If that checks OK:
- pull relay, install your jumper to turn pump on. Pumps running? Start engine. Connect a hand-held tach (hint: there are DVOMs with an engine speed function; can also use an accessory tach) to the "terminal 1" slot in the pump relay socket (it's the one tiny pin.) Read engine speed? Then line to coil is OK.
-- If both of these checks pass, then fuel pump relay has failed.


----------



## axe_ace (Jun 21, 2011)

*Update- Tach Signal Intermittent*



cuppie said:


> The pinout, friend, is printed on the relay (or, should be, if you still have an OE relay in there.)
> 
> And, the troubleshooting instructions are missing a step - the first step:
> Turn key on. Pump run yes/no?
> ...





Thanks Cuppie-

I have been operating vehicle with paper-clip bypassing relay and pulling the fuel pump fuse when stopped (to prevent discharge battery).

Had somewhere in the back of my mind decided someday to replace relay- without having made a solid diagnosis of whether it had really failed or not- either it would fix it or not- but while tinkering with other more pertinent problems (specifically spark plug wires someone had hacked and patched together- even though there were the makings of a compleat new set in the boot) 

Lo and behold while wiggling wires in the engine compartment my tachometer mysteriously started working again! (I can't recall it having ever functioned since I've had the car.) 

Somebody had done all manner of terrible things to the integrity of this car's electricals, but I've been very fortunate to have found this forum and the wealth of good advice and technical expertise needed to keep me going on the high road to getting this thing back in good operating condition.

Tomorrow- weather permitting- I plan on pulling the center console and on down to the air-blend door to hopefully duct-tape up the "swiss-cheese" holes I expect to find there. (I ran out of daylight before quite getting the center-console out today.) 

I am pretty sure now that I will also find my fuel pump relay to be good- just a problem with the tach side wiring at the coil.

I was on here actually looking for instructions pertaining to that when I came across your reply to my earliuer post- my Goldwing forum Goldwingdocs.com notifys me by email when there's been a reply to my post-= I guess I have my settings messed up here or something (?)

I'll try and post back tomorrow with some good news- I just wanted to thank you for aiming me inm the right direction, even if it wasn't timely response on my part!


----------



## axe_ace (Jun 21, 2011)

*Wealth of Pin-Out Data for Volkswagen Like Mine*

:wave: http://www.a2resource.com/electrical/CE1.html :wave:

I meant to put this link in my last reply- this exact page is what really got my attention back on to what my fuel pump relay was up to- don't remember how I came to have got there


----------

