O/T MX5 Post Engine Rebuild - Oil Pressure

[Graham King]

Folks, I know this isn't 7 related but hopefully someone can answer the following query.

 

Following a major problem with the engine in my wife's MX5, I have rebuilt and refitted the engine. It has not yet been started but in order to check I have oil flow etc I have been cranking it over on the starter. The car has an electric oil pressure guage, with 1 wire to a block mounted sender. On cranking this registers no oil pressure at all (it doesn't move).

 

Would cranking the engine on the starter be enough to register on this type of guage or will it require the engine running before registering. I obviously don't want to start the car until I know I have proper oil flow. Another possibility is that the sender has failed as the block was sent away for a rebore and was cleaned in the process. Can anyone let me know how I can check that the sender is working correctly.

 

Thanks for any advice anyone can give.

 

Graham.

 

R7 GPK

Superlight #85

[Dave McCulloch]

Graham

 

Apologies if I'm questioning the bl**dy obvious, but how long have you cranked it for? When I fitted a newly built K series into my seven, it took quite a long time cranking to register oil pressure on the (electrical) oil pressure gauge - probably 90 seconds to 2 minutes of actual cranking - done in 20 second bursts with a pause between each to avoid overheating the starter.

 

Dave

[Graham King]

Dave, a good question, I have certainly not cranked it for 2 mins at any one go, have done it for approx 20 seconds to avoid starter damage. Have tried on a number of occasions but usually separated by a period of time (say 30 mins or so) so I guess oil would have drained back down. Maybe I am just not giving it long enough.

 

Does anyone know if there is any way of testing the sender to see if it working or not?

 

Thanks for the reply.

 

Graham.

 

R7 GPK

Superlight #85

[Ged]

I know that on certain MX5's (MK 2's I think), the pressure gauge was simply on or off. The equivalent of a warning light, so there's a very good chance that cranking it over would not achieve the pressure required for it to spring to life. A search on http://www.mx5ocforum.co.uk/ should throw up confirmation.

[Graham King]

Cheers Ged, mine is a MK2 so maybe this is the case, I am going to remove the cam cover tomorrow and crank it over with it off and check oil is reaching the head successfully, if so will assume all is ok and try and start it properly.

 

Thanks.

 

Graham.

 

R7 GPK

Superlight #85

[Gridgway]

are you cranking without plugs to get a good cranking speed?

Graham

[I.Mupferit]

Something I have done in the past when faced with a possibly knackered oil pressure sender is to unscrew the sender from the block and hold a finger firmly over the hole whilst keeping away from rotating bits and get someone else to crank it on the starter. Make certain they are ready to stop cranking at your command as the oil will readily squirt out if you do have pressure.

 

Provided it passes that test then refit the sender and start up.

 

Oh, and crank it with the plugs out as Graham suggests.