Delco Moraine problems

[whatarehughlike]

I own a 1992 RHD chargecooled Lotus Esprit SE. This car is fitted with a Delco Moraine ABS IIIA braking system that has the following problem. From complete depressurisation it pressurises to 
186 Bar within 20 to 30 seconds of the ignition key being turned on at which point the pump cuts out, almost immediately the pressure falls to about 169 Bar. Turning the ignition key off and on at this point has no effect on this situation, however, on applying the foot brake, the pump is activated immediately and the pressure readings follow those described above. 

Looking at the manual related to the braking system these symptoms seem to fall into the category of “ E. PUMP OFF TIME TOO SHORT” (page 53 Lotus Service Notes Section JF). I have fitted a new accumulator and ABS switch recently and they are not defective. There are no external leaks in the braking system.

The possible causes of this presentation are described as being: “Excessive internal leakage ; low precharge accumulator; leaking solenoid(s); damaged master cylinder/booster assembly.” raising the following points:- 

Where could this “Excessive internal leakage” be lurking? 

Does leaking solenoid(s) mean that they are wholly defective or merely that the seals around them are leaking and if defective can they be serviced?

I feel confident in eliminating the accumulator as the seat of the problem as it is functions normally.

In view of the fact that the Pump off-time is below the lower level of 30 seconds, i.e. zero seconds in my case, as described on page 54 of the manual, said manual advises replacement of master cylinder/booster assembly!, presumably because  “there are no serviceable parts in the master cylinder/booster assembly” however, it appears to have been published in 1995 and, just as it states that there are no serviceable parts in the steering rack whereas there are now refurbished steering racks available for this car I was wondering, because of the elapsed time, if anyone out there has ever refurbished this component. 

I have also replaced the pressure relief valve but this has had no beneficial affect.

Has anyone come across this problem and if so what their course of action.

 

 

[Richard123]

I just finished battling a similar issue where the pump ran each and every brake pedal press.  I assume your ABS warning light is on if you drive?  And that the brake pedal pushes back against your foot during braking?

 

My problem was with the pressure switch that sits just underneath the accumulator.  Is that the "ABS Switch" you mention replacing?  (I couldn't find any sources for the pressure switch as the supply has apparently dried up.)

[OwenGT3]

I had no end of problems with my ABS system, but sorted it in the end. What new ABS switch have you fitted as they are no longer available? I have a two switch system fitted, but some people are now finding switched that can do both pressures switching. Also what accumulator did you get as some are different pressures, mine came from America and was the right part number, but i understand some other car makes do fit, but unsure of the pressure.

I got mine al working, then disconnected the solenoid switches with the resistor by pass mod, so now I have a good solid pedal and no ABS, so much better. If you are checking the system, it's worth getting a gauge and fitting to check all pressures, something I did as the switches don't always go on and off when you think they should.