kvr901

Hi,

Short preface: I used to be a mechanic (Porsche, Opel, MB, BMW, some Ferrari), but have been out of the car fixing business for 25+ years. So I am knowledgeable, but have forgotten a lot of the day to day repairing.

In 2000 I converted a 1987 Turbo to a GM 305 injected V8 with a GM T5 transmission. Nothing fancy. I enjoy the car, but don't drive it much. (4,000 miles in 18 years.) I drove it 1,000 this summer.

Since I built it, and to this day after several minutes if standing still idling (never timed it maybe 5 or 10 min) a beep starts and is approximately 1 per second, AND the power steering stops working. If I move forward OR backward several feet the beep stops, and the power steering returns.

I don't have any 1987 manuals, but I have my 1988 owner's manual and 1988 RX-7 factory service manuals (from another car I used to have). The 88 owner's manual mentions warning beeps, but nothing about beeps related to steering.

I can dig through this and probably eventually find it, but I thought one of you guys might know the answer.

TIA

kvr901

Above I wrote I thought the time was 5 or 10 minutes, but today I had a watch with me. It is closer to 2 minutes (at least today).

The only connections to the T5 transmission is the reverse light switch and a mechanical cable to the speedometer. My guess is once the speedo cable starts turning at the speedo there is some circuity in the instrument cluster that recognizes the car is moving (it only takes a few feet forward or backward... maybe 20 or 30 feet).

Anyone have any ideas why the beep and the stoppage of power steering if stopped for a couple of minutes?

Hot_Dog

Never had this problem on my S5, but maybe this link will help you: https://www.rx7club.com/new-member-r...eering-869542/

kvr901

Ah ha! Interesting. There is a speed sensor in the speedo, or the instrument cluster.

Okay... now I will have to research how the system worked with the Mazda engine, and try to make it think it is still dealing with a Mazda engine at idle.

It's a start. Thanks.

_NGL

http://www.rotaryheads.com/PDF/2nd_g...stem_part1.pdf
15-85 shows the failsafe modes for the power steering ecu.

It's interesting that you lose power steering in your swap though, did the GM 305 also have speed sensing power steering?

the speed sensor in my cluster had an issue and it would beep once, pause and repeat after I drove the car higher than 2200RPM for more than 80 seconds.
I disabled the RPM signal going to the power steering ecu and all was well. No beeps, power steering still active.
Give that a try?

kvr901

I don't know if the 305 had anything related to power steering. I'll have to double check my wiring diagrams etc.

Thanks very much for that extra info. It gives me some direction to explore.

mazdaverx713b

iTrader: (91)

The 87 and 88 RX-7's used engine speed to determine power steering pressure output, not vehicle speed as in the 98-91. There should be no sensor on the speedometer that's related to the power steering system. The pressure switch is threaded into the power steering pump.

kvr901

I will have to check into this. Revving the engine does nothing to stop the beeping or reengage the steering on my car. However, driving it forward or backward several feet (20-30 never measured) turns off the beep and brings back the power steering.

When installing the V8 nothing was changed about the steering pump, plumbing, or electrics.

Hot_Dog

The S5's used both engine and vehicle speed sensing PS depending on the model. The S5 GXL and GTU both used engine speed PS. The S5 GTUs and TII both used vehicle speed PS. Case in point, my 90 GXL has engine speed PS.

I believe all S4's all had vehicle speed PS. Reference Post #8: https://www.rx7club.com/2nd-generati...-pumps-533982/

kvr901

Ooooh! You just opened a bag o' worms for me with that link , but thanks again.

I used to have an '88 SE (bottom of the line RX-7). After using it up I stripped the car, sold the shell, and kept a bunch of parts. The '88 P/S pump and steering gear I kept as spare parts for the '87 Turbo (now V8). Maybe those won't even be usable for me in the future. I will have to look into this too.

Hot_Dog

The 88 PS pump and the 87 Turbo (now V8) PS pump are both vehicle speed sensing PS pumps. They are also identical pumps. If you checkout Rockauto's website you will see that both these PS pumps have the part number (i.e., ACDELCO 36P0655 {#19319181}).