Fuel Pump Relay Replacement Prototype

Post by **MrAl** » 17 Dec 2022, 05:09

Hello there,

Here is the start of the v70 1998 fuel pump relay replacement using just a single 8 pin microcontoller.

Just for reference, picture #1 is for a clock calendar but it could be used for the replacement also.
Picture #2 is the board i would use for the chip and you can see the chip is so small at the farther end of the board in the dark green socket. It's the 8 pin chip and i put a dimensional guide on the side so you can get an idea how small it is. The chip is about 0.5 by 0.4 inches and only about 0.2 inches high.

This chip can replace the entire guts of the fuel pump relay with just a tiny bit of coding work. A few resistors and a couple cheap capacitors would also be needed, but the entire thing could be as small as 1x1 inches. I think that's amazing how technology has changed.

There is just some more research that i have to do to find out how the reliability of the new design would compare to the older design especially since it will be subject to higher than normal temperatures being in the engine compartment.
One of the key points about reliability is the total number of connections in the circuit. This chip and circuit would have about 10 connections while the original relay design has about 100 (roughly). That's one tenth of the number of connections so that's a good start.
The only thing is i have to compare the reliability of the chip itself to that of the chip on the original relay board. The chip on the original i think has very high reliability it's considered a workhorse in the industry, or at least it was. But that says a lot about the reliability. That means nobody is afraid to use one in their product.
Now the microcontroller chip is reliable too but it also has flash memory that is programmed as any flash memory would be. I am wondering how well that will stand up in the higher than normal heat of the engine compartment.

It sure is interesting and tempting to change it out though and see how it goes over several years.
As others have mentioned also it would be interesting to add some features like monitoring the battery voltage and possibly current and storing the results.

Some food for thought and any ideas would be appreciated of course.

After i posted this i realized there could be a keypad like that shown in the second image, and the keypad could be for code entry. Enter the wrong code (pin) and the car wont start (due to the uC chip preventing fuel flow).

Post by **scot850** » 17 Dec 2022, 05:29

Where the fuel pump relay sits in the fuse box, I would not expect it to see any real issues with temperature from the engine. It may be a bigger issue in hot external temperatures.

Neil.

Post by **volvolugnut** » 17 Dec 2022, 08:03

Does the second photo show the pull rope for emergency starting?

volvolugnutr

Post by **abscate** » 17 Dec 2022, 09:28

I think there is a syntax error in that string of code….

Post by **MrAl** » 17 Dec 2022, 09:49

volvolugnut wrote: ↑17 Dec 2022, 08:03 Does the second photo show the pull rope for emergency starting?

volvolugnutr

Hi,

Ha ha. Yes that is to make sure the ZIF socket does not get lost, again. It was about 10 bucks and i already lost one because it fell out of the regular socket underneath. I could not solder it in because the board was double sided and i didnt want to take a chance on losing a connection when replacing it. So if the ZIF (zero insertion force) DIP socket falls out again, it will just dangle on the end of the string.

Post by **MrAl** » 17 Dec 2022, 09:52

abscate wrote: ↑17 Dec 2022, 09:28 I think there is a syntax error in that string of code….

Hi,

Hey didnt you know? A world without string is Chaos.

The Inca used to use knotted cord to record things because they had no way of writing, i think it was circa 1400 or something.

That string keeps the ZIF socket from getting lost again as it can fall out of the regular socket underneath it. I lost one already didnt want to lose another. And just in case i want to take it out, i can just pull it out of the socket underneath.
Those sockets are nice though there is no force required to place the chip in the socket so no risk of bending pins or any extra stress on the interface between the lead and the body of the component. It's a lot bigger than the chip shown because it can handle larger chips too with more pins.

Post by **abscate** » 18 Dec 2022, 01:51

A good piece of string will cost the same as the replacement fuel pump relay, and you don’t have to ask how long it is, either. I know some experts on string theory who might appreciate the gravity of this situation.

Post by **MrAl** » 18 Dec 2022, 06:19

abscate wrote: ↑18 Dec 2022, 01:51 A good piece of string will cost the same as the replacement fuel pump relay, and you don’t have to ask how long it is, either. I know some experts on string theory who might appreciate the gravity of this situation.

Hi Steve,

Yeah when i started work on the fuel pump relay troubleshooting i did not realize that FCP gave a lifetime guarantee that's quite a nice motivator to buy one. Oh i also wonder how long it takes to ship one here to NJ.

I did learn a lot about it though that turned out to be very interesting. It used a chip i had been familiar with (and entire logic family) for a very long time so i found that interesting too. I also learned the functionality of the circuit which also was very interesting.
Now i am just into it for the hobby value of it. I may never program a chip to do the same as the circuit, but it is interesting to think about and if i get into it after i do some other things i may just make one. As i was saying though, i have to compare the reliability of the original to the new before i would dare put it in my car or anybody else's car.

Hey that's funny, string theory and gravity, both a play on words. Just got that

Post by **wizechatmgr** » 19 Dec 2022, 10:16

I'm not sure which microcontroller family was used, but WabTec used to manufacture speed sensors for trains. They had to be shake and bake tested. The gentleman I would ask is sadly dead. I do know that even then, it wasn't unusual to have one of two out of a batch of ~100 not make it. Sadly as the company started collapsing, they started shipping bad units, leading to eventual derailments across at least North America, if not the world.

Post by **MrAl** » 19 Dec 2022, 16:31

wizechatmgr wrote: ↑19 Dec 2022, 10:16 I'm not sure which microcontroller family was used, but WabTec used to manufacture speed sensors for trains. They had to be shake and bake tested. The gentleman I would ask is sadly dead. I do know that even then, it wasn't unusual to have one of two out of a batch of ~100 not make it. Sadly as the company started collapsing, they started shipping bad units, leading to eventual derailments across at least North America, if not the world.

Wow that's sadder than sad. I hate hearing about that kind of stuff the companies should have the integrity to just close up and let it be.

Yes shake and bake is a good way to put it. I could use SMD parts that withstand better vibration i think because of their lower mass.
I am still thinking about this right now i am trying to revamp my wireless automobile voltage monitor. I want to be able to monitor the voltage form inside the house. For an update im just going to have it transmit wirelessly and be done with it. Last time i used blinking LEDs you can see out the window of the house ha ha. The blink pattern would reveal the current battery voltage.