TR FUEL PUMP

Well, of course, replace the relay! The current is so high, even when things are working as they should (~10A), that a very small resistance (like ~0.5 ohms) at the contacts inside the relay, or from the relay male tabs to the fuse-relay panel female sockets, can cause it to overheat (because 10A x 0.5 Ohms = 5 Watts of power).

Remove the relay and touch the leads of a (high current capable) DC ammeter from the (vertical) 30 terminal in the relay socket to the bottommost 87 terminal in the relay socket -- this will cause the fuel pump to run (even with the key "off"). If the current isn't more than 10~11A, and the pump isn't making horrible noises , then the pump is quasi-OK.

If the new relay "fries" again (or as a preventative measure) -- try "squeezing" the female tabs on the fuse-relay panel to get a better grip on the male tabs of the relay.

 

Steve M,
While you guys are on the subject of relays, could you explain the terminal functions in relation to terminal I.D.'s on the relay.
Even after looking at the diagram on the side of the relay I am not sure of the high and low voltage pathways.
Any help would be appreciated.

Thanks!
DJ

Terminals:
87 =
87a =
86 =
30 =

 

You must be looking at a ...101 relay (since that's the one with an 87a terminal).

85 & 86 are the ends of the coil winding inside the relay that cause the relay to actuate -- whenever this is +12V, a small ~150mA current flows, and the relay actuates

87a = this terminal is connected to terminal 30 when the relay is unactuated (i.e., no voltage on 85-to-86)

87 = this terminal is connected to terminal 30 when the relay is actuated (i.e., there is +12V between 85 and 86)

So terminals 30, 87a, and 87 are the ones carring the large current (30 connected to 87a or 30 connected to 87)

They tried/try to "standardize" the terminal name and function on the various electrical gizmos (e.g., something that is +12V when the key is in the start position is always called terminal 50; something always +12V is terminal 30, something +12V with the key "on" is terminal 15, etc.), but they often make little cheats (like putting the +12V always on terminal 87 and using terminal 30 to go to the device the relay is controlling). I think I have the whole table in a Bosch publication somewhere -- I'll scan and post if I can find it fairly easily .

 

I was at work when I posted last so called-out the terminal designations from fuzzy memory.

Thanks for the explanation of the terminal functions. I knew terminals 30 and 87 were key delivery but was unsure as to what the additional terminals were for and what they were supposed to be hooked to, i.e. signal voltage etc.......................

Again, thanks for the info. It will come in handy when I build the auxillary bank of relays for the cooling fans and fuel pumps.

 

I've just had the same issue, go out for a long run and then the pumps seems to whine noisier than normal and then try again next day and all seems fine. Ive checked the relays and they are all good, no signs of scorching etc. Any thoughts on this gremlin?

I do have the new fuseboard to go in (winter job) but this is something new that's just occurred.

 

I would put the new fuse board in now! I got mine from Guido, for the 512tr and it was plug and play. I could quite literally do the job in less thatn 2 hrs if I had to.

 

Another important point is to address the root cause for the high current: the (presumably) old fuel pumps. A preventive maintenance swap to new Bosch units is highly recommended (and very affordable).

I have found the factory circuit board to be fully functional with cleaned contacts, swapped pumps and new relays....

 

Well I decided to make a start on the fuse board replacement and glad I did as its a bit of a mess with many previous repair attempts made and lots of scorch marks, especially those for the fuel pumps! Not sure anyone could a replacement in 2 hours though with having to crimp all those connections, I managed just the fuse board replacement and lower 2 white connector replacement in 3 hours, maybe its the age and numb legs!

Ordered new pumps also they were quite reasonable. Lets wait and see!

 

Which fuse board did you purchase? On the 512 tr Guidos is plug and play. On the Testarossa I think you have to modify the white connectors!!!

 

Yes its Guidos, each wire has to be re-crimped onto larger fittings. 6 more white connectors to go!

 

And for what it's worth: When I replaced my fuel pumps from ebay the pumps are part number 121727 (for my 86) and they are $182 or you can buy them from someone posting the exact picture of the black body for $290 but you will receive the un-painted version.

Sometimes people fib on ebay.

Jeff Pintler
89 348tb, 86tr, 99 360 3-pedal

 

I purchased original Bosch made in Czech Republic. on Amazon 69435 002 091 97 01. For my 87 TR. Real cheap!

 

I had same issue with LH fuel pump. It was the fuse box. Burned out connectors. I ordered a new one from Guido. The car is now running perfectly.

 

Just ordered 2. Thanks for the tip.

 

That Bosch 69435 pump will probably work OKish (with the black spacer to fit the mounting clamp), but it has a smaller body, and, therefore, a smaller roller pump head diameter than the OE TR fuel pump (and may run out of volume delivered at high RPM):

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Bosch 69532 is more the OE fuel pump for a TR (also available at amazon):
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After reviewing the numbers in the TR WSM (and some measurements I've made in the past), I'll reduce my level of concern when using the Bosch 69435 pump (but would still buy the Bosch 69532 pump if given a choice).

What's required = the TR WSM list the individual injector flow rate at "full load" as about 150 cm^3/minute. So for a bank of 6 cyls = 900 cm^3/minute

What's available = the TR WSM specifies the fuel pump for each bank deliver at least 1L in 30 seconds (when providing the regulated supply pressure -- i.e., what comes out the return line from the pressure regulator going back to the tank when the engine isn't running) = minimum 2000 cm^3/minute. IME, a fresh 69532 pump and a new filter might deliver 1L in 25 seconds = 2400 cm^3/minute (at the battery only voltage, not the alternator engine running voltage). Of course, the designers need to allow for a fuel filter starting to trap debris, the pump head itself wearing/leaking internally over time, the electrical system maybe not delivering full voltage, etc. so the 2000 cm^3/minute minimum makes sense and gives about a 2:1 factor of safety compared to what's needed (which seems conservative).

If someone has measured the time required to have 1L come out of the return line from the pressure regulator when the engine isn't running with the Bosch 69435 pump (or how much fuel comes out in 30 seconds), please post -- would be interested to compare it to my Bosch 69532 measurements.

 

in my competition I put in fuelpumps that can deliver 6 ltr /minute at 5 bar. I tested before I installed. I used pierburg pumps (but don´t know the anymore) . have most of my documents at home and not here in thailand.

sorry, pdf only in german

I once counted the max fuel consumption for my car with 1,5 bar. and I would need for 100 km 100 ltr fuel. so when I would go 1 hour with max. speed 400 km/h I would need 400 ltr fuel in 1 hour. so each bank 200 ltr each hour. in 1 minute then around 3,5 ltr. and so I was looking for fuel pumps what can deliver minimum 4 ltr each minute. those what I have now are a little bit longer than original, but also thinner in diameter.

 

Why not put 2 fuel pumps for each banks like Mercedes sistem.

 

where you want to put near the fuel tanks 4 pumps?

 

That does seem a little crazy having two pumps in series, but isn't that for larger displacement W124 engines (larger than the 2.5L of a TR bank)? Probably didn't have a single pump available that was large enough (and, I believe those later MB CIS systems went to an even higher fuel pressure KE3-Jet).

 

300 series in that video is 3 lt. So only 0.5 lt more. Instead of the 2 pumps now for each bank, a 3e pump in serie with the 2 others can help. There should be enough place for a 3e pump beside the 2 others. Its just an idea ....I think aloud.

 

when I got my competiton koenig had put in a 3rd pump. but only for the additional fuel for his "lenz-turbotronic". so when the boost increases 0,3 bar