Hi all,

MY 1985 RoW 16v Manual

Some Rennlist guidance would really help..thank you

Lots of fuel issues when I bought the car (5 years+ ago) so replaced damper and regulators and vacuum lines (will come back to that) finally identified as a wrong temp sensor. car ran but engine flooded easily. I also started getting lots of fuel going down into the sump. Lots more time passed and found that PO had put a hard ground to the fuel pump so it was always on...arghhhh unbelievable.. removed that and all running nicely on driveway.

I have been doing a front to back refresh of the car which included dropping the fuel tank but when re assembled no start... fuel pump had died and would just get hot.... so replaced the fuel pump and engine ran again. Slight concern as fuel pump was really loud but put it down to not being a particularly expensive one. Now the car was fully back together (did the full sump seal, engine mount, steering rack refresh job) i headed out for a test run. all going well for 2 miles, Some smoke on down shifting a bit of stutter then engines dies.

Fuel pump had died again - tested with direct power and a few taps to try and release it but it had gone.

So my latest theory is: When i replaced my regulator vacuum lines i used soft silicon ones instead of hard lines, i am guessing (it is just a guess and happy to be put straight&#128591 that on down shift the vacuum is increased and collapses the vacuum lines which some how increased the pressure in the fuel system which over worked the fuel pump trying to push in more fuel and burnt out the pump.

Getting some new vacuum lines this week (and a new pump) to test the theory.... Or i have picked up some rubbish from the tank into the pump and killed it....

Any thoughts comments greatly appreciated..

Cheers

David M

P.s My 928 has taught me an important but frustrating lesson.. “Never ever assume a problem is caused by just one thing” 🙂

 

David,

The silicon hose you used may well collapse and that would cause the fuel pressure to run about 10 psi higher than it should thus run a bit rich but nothing that should cause any major issues- for sure the pump should not be burnt out so I would think something else is going on.

I take it your model year does not have an in tank pump- that being the case have you pulled the strainer to ensure it is not full of crap or house bricks and thus blocked? If the strainer is blocked at some degree of blockage the pump will cavitate and then for the pump it is game, set and match rather quickly- hopefully not the case but if you have had one go and then another in rapid succession I would be suspecting something along those lines.

Folks are often very cagey about pulling the strainer because of the possibility of the insert turning and wrecking the tank. If you do decide to pull the strainer there are precautions that can be taken to minimise the possibility of the insert turning thus why it is prudent from time to time to pull the strainer and with correct torque hopefully help ensure future removals will go unhindered.

 

^^ The strainers also have a habit of falling to bits over the years.

Those small pieces of plastic could be what is jamming your pumps up.

I would do what is recommended above and remove if not replace the strainer along with a fresh seal and new strainer to pump hose.

 

Good advice.... The fuel level is low at the moment so draining the tank inspecting the filter and likely replacing the bottom connection and filter is worth doing....most of the work I am doing is so that the car can be easily serviced in the future..... I know there are risks in removing the filter and connection so will read up around this first.

How important is it to prime the pump and filter on the 928? I didn't do this, could this have caused an air lock?

 

Simple answer- no. The pump self primes.

 

Based on your report I would replace the fuel strainer this should be done when fitting a new pump and replace the fuel injectors

 

^^^ What Stan recommends, plus a new fuel filter too.

 

I burned out 2 pump relays before I found a poor contact at the fuse - old bullet style. If you have these fuse types, suggest you pull all fuses one at a time, clean the contacts and the fuse ends, apply Deoxit. My pump pulls ~7A. I also saved a pump once by applying reverse voltage, and it spat (past tense of 'spit' in most english speaking countries) out an obstruction and lived for several more years.
jp 83 Euro S AT 57k

 

I'm going to "fix" this, a little bit:

NEVER install a new fuel pump without draining the tank and checking/replacing the strainer!(Or, for certain years, the intank fuel pump.)

We (my son, Kyle) recently "rescued" a client's vehicle hours away from us (in beautiful Bakerfield) which had a fuel pump failure.

I sent him prepared (not wanting to take a chance), and he drained the tank (full) and replaced the strainer, in the motel parking lot.

A restricted strainer/intank pump can kill a new main pump, very quickly!

 

My 81 started to have intermittent fuel pump issues, turns out one of the female spade terminals for the relay had pushed back and wasn't making good contact with the relay. Just something else to check on the fuse panel. Not a bad idea to take a test wire with a male spade terminal, and see how tight the connectors are.