How to Convert 1-Coil Tach Signal to 4-Coil Signal for Distributorless Ignition System?

ok so here's my problem. I installed a tachometer on my car which uses a distributorless ignition system so instead  of getting the correct signal to my tach I only get a quarter of the signal because I can only connect to one of 4 coils/ fuel injectors. There is no other tach source and the only other way would be to somehow read a digital signal given by my ecu and translate that to a 12volt signal which is way out of my league. I don't know much about this stuff and I could really use the help because this has been driving me crazy. My question is that isn't there some sort of transistor I can put inline that will just take the power input and multiply it by 4 and output that voltage? That way whatever power sent in would be multiplied by 4 and out to my tach giving it the correct reading for all rpm's? I know it's not as simple as that but there's got to be something right? And if so could you kindly please tell me exactly what I need?? MUCH thanks in advance for any help given by you electrical gods!

That is expected since the tacho is getting a signal from only one injector. You need to simply multiply the tacho reading by the no. of cylinders to get the correct RPM.

Sorry - not multiply by no. of cylinders but multiply by 4 (assuming its a 4-stroke engine)

Basically you need a pulse or frequency counter - count the number of pulses in one second, multiply that by 4 to get the total RPS, and then by 60 to get the RPM.

So would one of those output the correct signal for me? Because my tach does not have the option to multiply it for me so I need whatever I hook inline to take that signal multiply it by 4 and send out that new signal that I can connect to the tach

No - you need to count the number of pulses, and then multiply that count. If you have a frequency counter, multiply its readout by 4 (with this there's not much you can do apart from multiplying whatever number you see on its readout). If you want to display the multiplied number then you will need some sort of frequency multiplier and that too one that can be programmed to multiply by a given amount. The other option it to build it yourself using a microcontroller - count the number of pulses in one second, multiply by 4 (or whatever) and send that number to the display.

You can easily double the frequency of a pulse using an XOR gate. With judicious choice of RC values you can use the second of the 4 gates in a CD4071 package to double the two to give you 4 pulses (see attached diag).

The length of the pulses may end up be too short for your tachometer, but without the specs you have no way of knowing. The advantage of this over a micro is a) no programming and b) the 40712 will run at 15VDC, so at your car's 12V an c) it is easily available as a through-hole component. However a micro could stretch the pulse with greater ease than fiddling with capacitor values.

Please protect the device against over voltage and noise and make sure the unused inputs are all at a defined voltage- ground is probably best. In fact I would be tempted to parallel the two remaining gates to boost the output drive current as shown in the attached file.

here's a link to the 4071
http://www.ti.com/lit/ds/symlink/cd4071b.pdf