General Troubleshooting Lesson Learned

edspringer

Registered User
As some of you have read recently in other posts, an $8 relay cost me about $160.

Problem: SC may or may not start. It would start almost everytime on the first try when cold. However, once run and warmed up, it may start on the first try or the 15th try and when it did start, it would continue to run with no cutouts or misses. Before this no start happened, I noticed it was hard to start after it warmed up but it would start normally on the first try. I wrote this off to vapor lock in the fuel rail. Also, it would seem to start easier just when I started to slightly release the ignition key. So the first thing I replaced was a $30 ignition switch. Did not fix. Then I checked for spark. Plenty of spark so the coil and ICM were OK. Then I checked the fuel pressure. When I cycled the key, sometimes there was 40 PSI and sometimes there was 0 PSI. Finally, I found the problem and checked my wiring diagrams. I thought the fuel pump relay was bad and that is located in the IRCM. I had a spare IRCM from a previous troubleshooting experience. So I replaced that. No fix. I went to the junk yard and got another inertial switch and installed. No fix. So then I thought the fuel pump must be intermittent. Bought a new fuel pump assembly for $130, dropped the tank and installed. No fix. So I looked at my wiring diagrams again and noticed the Electronic Engine Control provides the ground for the fuel pump relay in the IRCM. I grounded that wire and instant fuel pressure. So I looked at my relay setup from the owners manual and swapped the ABS and EEC power relay since they are the same. Started everytime. So I did a little preventative maintenance and bought 2 new small and two new large relays and installed.

After thinking about what happened, I can understand why it happened. I took apart the bad EEC power relay and found the contacts were burnt. There was no major contact pitting, just enough black residue on the contacts to prevent good contact. A little TLC with some emery cloth and now I have a spare. Some things to consider about relays. These relays are designed to operate at 12 VDC. When starting the SC, the voltage drops to about to 9 volts, reducing the coil magnetic field strength and decreasing the pressure on the contacts. I attribute this to the reason why it would start easier when I released the ignition key easy allowing the 12 VDC to increase contact pressure. Also, these are electro-mechanical devices and over time, with the hundreds to thousands of on-off cycles, the coils will become weak and the contacts will burn due to the current arc produced during each key cycle.

A recent experience with my Excrusion is another example. My interior lights are on a timer that controls the "delay" relay. After I shut the door and 15 seconds later, they are suppose to go out. Well, they stayed on. This forced me to remove the instrument panel, cut the appropriate wire and install a circuit breaker so I could turn on the lights when needed. I swapped relays in the panel that has about 10 relays installed and it worked for about 2 days and then the same problem. Went and bought a NEW relay and problem solved. Since the relay swap did not fix the problem, I'm going to eventually replace all of the relays for preventative maintenance reasons since the EX has 61,000 mile on it.

BOTTOM LINE: If you are experiencing hard starting or non starting issues I encourage you to take the approximate 2 minutes it takes to swap the EEC and ABS relay to determine if the EEC relay is bad. These cars are old and I'm sure not a lot of attention is paid to these 4 relays. Believe me, in my case, it would have been a real cheap fix!

Ed

’94 SC Red Auto: 110,000 Miles, Headers, No Cats, Pro Torque 2500 Stall Converter, TRANSGO Shift Kit, 10,000 Lbs Auxiliary Tranny Cooler, Tranny Fluid Temp Gauge, 3.73 Gears, 70mm BK Throttle Body, 76mm C&L MAF with Gold Tube, A/F Ratio Gauge, Raised SC Top, Teflon IC Seals, ’90 XR7 SC Pulley, ARP Head-Rod-Main Studs, Scorpion 1.73 Roller Rockers, Solid Motor Mounts, Iridium Plugs, Live Wire Plug Wires, Screamin’ Demon Coil, 36# Accel FIs, Custom Air intake, K&N 9” Cone, Royal Purple Synthetic Lubricants and Optima Yellow Top.
 
I have found with these cars, a good, dependable multi-meter is a must-have tool for troubleshooting. I have a meter from MAC Tools and it meaures down to the the smallest of milivolts and miliamps and can detect excessive current draw and drain across a relay which will tell you right away if there is an issue with the part in question.

Another important step to remember when troubleshooting is to go for the simple part first if you have no choice but to swap out parts. Sometimes you are relegated to this method simply because it's virtualy impossible to figure out what part is the cause for the problem you are experiencing.

Being able to decipher wiring schematics, especially with these cars is of the utmost importance. With all the relays and electronic components our cars have, to be able to read a wiring diagram and be able to tell a relay from a resistor goes a long way in finding out what a malfunction might be.

Good info and thanks for the heads up regarding the relays in question! ;)
 
As some of you have read recently in other posts, an $8 relay cost me about $160.

[So the first thing I replaced was a $30 ignition switch. Did not fix it

I don't see where you put the old ign. switch back in...? Why didn't you return the ign. switch for a refund to help keep the parts tossing down?

Is it possible you had more than one issue and the relay was simply the last one fixed?

Not all SCs have the same relay configuration as I understand. What year is the car you worked on in this example? '94, right?
 
I don't see where you put the old ign. switch back in...? Why didn't you return the ign. switch for a refund to help keep the parts tossing down?

Is it possible you had more than one issue and the relay was simply the last one fixed?

Not all SCs have the same relay configuration as I understand. What year is the car you worked on in this example? '94, right?

No return on electrical parts. Got a good used ignition switch 4 sale!

No, the issue was the fuel pump was not turning on everytime I turned the key to on. I hooked up a fuel pressure gauge and watched it as I turned the key. When I had pressure it would start right up. No pressure, no start. That lead me to an intermittent fuel pump. After replacing the pump and no fix that is when I traced the EEC relay problem. When I replaced the relay, the problem went away.

You may be right and mine is a '94. I had a '90 XR7SC and not sure of the relay config under the hood. I thought the '94 was the same as my '90.

Ed
 
I thought the '94 was the same as my '90.

Ed:

See pic of my 1990 35th Anniv. SC below. Is this the group you're talking about...next to the battery, under the hood, on the left?


I paid $20.00 for a new 'Standard' ign. switch recently.

<a href="http://picasaweb.google.com/KentidCN/35thAnniversaryFordThunderbirdSuperCoupe/photo#5179157143618677970"><img src="http://lh5.google.com/KentidCN/R-AP-1VRbNI/AAAAAAAACWI/Hr7MlHv-oOA/s800/Fuses_relay_underhood.jpg" /></a>

Ken
 
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