No fuel delivery on my 86 project

**peterlund** · #1 (**permalink**) 10-17-2008, 11:17 PM

Ok. Found: severed flywheel sensor wire. Replaced sensor. Checked out Both sensors, and they are within tolerance ohm-wise. Traced down the sending wire at the coil, and found a fuse in there... all corroded etc... fixed that gremlin. Cleaned all grounds. Checked and cleaned all fuses in the fuse box. Checked and by-passed for now the fuse for the fuel pumps. Still... When I try to start her I do not get power to the pumps. Pumps work when jumped, so the problem lies within the wiring/relays etc. I have made sure air leaks are in check, and have a good strong spark. Where is my next logical avenue? Car has a strong battery, and is ready to rumble other than fuel delivery. No inertia switch on firewall. Suggestions? As always, Thanks!!!

**papajam** · #2 (**permalink**) 10-18-2008, 06:09 AM

1. At the fuelpump relay (drive relay), check for battery voltage at terminal #30. If no voltage, repair power loss problem from battery (wire, inline fuse, etc). If battery voltage, proceed to next step.

2. Check for cranking voltage at fuelpump relay terminal #50 with the key in the start position. If no voltage, repair power loss problem from ignition switch. If voltage, proceed to next step.

3. Check for cranking voltage at fuelpump relay terminal #87 with the key in the start position. If no voltage, replace fuelpump relay. If voltage, repair power loss problem between fuelpump relay and fuelpumps.

**peterlund** · #3 (**permalink**) 10-18-2008, 07:49 AM

Thanks Jim...
Off to the garage.... wish me luck.

**ghnl** · #4 (**permalink**) 10-18-2008, 07:55 AM

Just a thought (keeping in mind that electricity is NOT my strong suit) - you may want to check for power (i.e. voltage) using a 12V light bulb vs a volt meter. If I understand it correctly, a voltmeter can show 12V even when there are not amps flowing to actually power on whatever device you are having problems with (i.e the fuel pumps). Thus, the voltmeter could mislead you into thinking something is OK when it ain't.

**peterlund** · #5 (**permalink**) 10-18-2008, 08:10 AM

Quote:

Originally Posted by ghnl

Just a thought (keeping in mind that electricity is NOT my strong suit) - you may want to check for power (i.e. voltage) using a 12V light bulb vs a volt meter. If I understand it correctly, a voltmeter can show 12V even when there are not amps flowing to actually power on whatever device you are having problems with (i.e the fuel pumps). Thus, the voltmeter could mislead you into thinking something is OK when it ain't.

**peterlund** · #6 (**permalink**) 10-21-2008, 02:22 PM

Ok! After finding all the above mentioned failures, etc... I went about the simple three step diagnosis that Papajam posted. I also was lucky enough to receive from same a wiring diagram which also helped. The power to drive relay terminal #30 had 12V. The cranking voltage on 50 and 87 were under 1 volt. Now I really did not know what was meant by cranking voltage, but I thought that the amount was severely low. I have a bunch of parts from deceased Spiders, so I scrounged up a new relay... plugged it in and she fired right up... Then of course immediately died, but at least I have a common problem. I will go through he rest of the diagnostics and see what else I can find. Amazing that I had almost all of the issues I could possibly have. BTW, if I blow into the majority of the vacuum lines on the engine while plugging the opposite end I definitely have leaks as it does not have pressure resistance. How much of a vacuum leak does it really take to get to the dreaded start then stall scenario??
Oh well... back out to the garage. Wonder what else i can find.
Thanks again to all.
Peter

**papajam** · #7 (**permalink**) 10-21-2008, 02:33 PM

Quote:

Originally Posted by peterlund

The cranking voltage on 50 and 87 were under 1 volt. Now I really did not know what was meant by cranking voltage,...

**peterlund** · #8 (**permalink**) 10-21-2008, 04:42 PM

Quote:

Originally Posted by papajam

Cranking voltage is system (or battery) voltage when the starter is engaged (cranking the engine) hence the term 'cranking voltage'.

autoxsteve · #9 (**permalink**) 10-21-2008, 04:59 PM

test your aav. you might be surprised how that can affect the engine from running.

**Slash** · #10 (**permalink**) 10-22-2008, 09:56 AM

Peter, if your Spider still won't run after you sort out the AAV, double- and triple-check the grounds. I went through this recently and was absolutely sure that the grounds were solid when I found one that had not been reconnected. There are four bundles with a total of seven ground wires on my '88, as can be seen here.

**ghnl** · #11 (**permalink**) 10-22-2008, 10:59 AM

Quote:

Originally Posted by peterlund

What is my next logical step? I know I have some (if not all) poor vacuum lines, but nothing that could be sucking straight air...

As I asked before, can the small leaks from all the vac hoses really cause this start/stall issue??

**peterlund** · #12 (**permalink**) 10-22-2008, 03:17 PM

Quote:

Originally Posted by ghnl

The L-jet is very sensitive to 'false air' (air leaks in the intake &/or vacuum hose systems). The L in L-jet stands for 'luft' - German for 'air' - make sense now?

Can you confirm that the fuel pumps remain powered 'on' when the engine runs for those few seconds? When you first switch on the ignition the pumps should briefly be powered on. Then when you turn the key to 'start' they should be on. Finally, when the engine is cranking/running (ignition firing) the drive relay sees that 'tachymetric' signal and keeps the pumps powered on. (this also functions as a safety measure - should the engine stall the pumps will not continue to pump fuel)

If the drive relay is not supplying power to the pumps then it might run for a few seconds on residual fuel pressure in the system.

**ghnl** · #13 (**permalink**) 10-22-2008, 03:29 PM

Silicone hose kits from Hi-Performance Store (scroll down about 1/4 of the way).

The vacuum hose kits do not include the 4 short intake hoses. Those are also available in silicone from Hi-Performance Store (same link as above) and from the usual suppliers (in standard rubber hose I assume).

**peterlund** · #14 (**permalink**) 10-22-2008, 07:51 PM

Just for an opinion or two... Here are the pictures of my plenum hoses... I am not 100% certain they are leaking yet, but I will change them out to be certain. I ordered a new set from Rayce, and a silicone set for the rest of the vacuum lines from Hi-Performance. BTW If anyone has tips on the intake manifold removal technique I am all ears!

**ghnl** · #15 (**permalink**) 10-22-2008, 08:02 PM

Quote:

Originally Posted by peterlund

Just for an opinion or two... Here are the pictures of my plenum hoses... I am not 100% certain they are leaking...