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Turns over will not start ran last night would not start in…

Customer Question
Turns over will not...

Turns over will not start ran last night would not start in morning

Mechanic's Assistant: Have you checked the battery, particularly the terminal connections? Are they corroded?

New battery

Mechanic's Assistant: What is the model/year of your Jeep?

88 wrangler sport

Mechanic's Assistant: Are you fixing your Wrangler yourself? What have you tried so far?

New coil new cap and rotor

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Its getting fuel

Submitted: 4 months ago.Category: Jeep
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Answered in 1 minute by:
12/6/2017
Jeep Mechanic: Matt, Engineer replied 4 months ago
Matt
Matt, Engineer
Category: Jeep
Satisfied Customers: 22,932
Experience: Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
Verified

Hello and welcome to Just Answer

1st check for spark by removing one of the spark plugs and plug it back into its lead and rest it on the metal of the engine ( DO NOT hold it on place by hand) then have your assistant turn the engine over whilst you watch the plug. It should give a fat blue spark at regular intervals.

If not then check that there's power to the coil pack (at the other end of the plug lead) using a meter. If there’s 12V at the pack but no spark then check the ECU power supply (fuse and relay) and also the connections to the crankshaft speed sensor.

If this is OK then check that the injectors are bing operated by the ECU, its hard to hear them ‘clicking’ with back ground noise so if you use a screwdriver like a stethoscope with one end placed against the body of the fuel injector while your assistant cranks the engine

The injectors should ‘click’ as they are cycled on and off

If you can't hear anything check the ECU power is present by measuring voltage at the fusebox and on its relay socket if OK then check the connections to the crank speed sensor and consider replacing this sensor if the wiring / connections look OK

If the car will start using a squirt of quick/ easi start into the intake then this confirms the problem is lack of fuel

Also its worth checking that the electric pump that feeds the injectors is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If you remove the filler cap to the fuel tank and listen inside while your assistant flicks the ignition you should hear it clearly

If the connections to this are corroded or damaged then the pump could stop at any time. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse, ideally measure the voltage at the pump and check its getting 12V.

You should be getting around 3 bar measured at the injector rail check to see if the plugs are getting wet indicating fuel is flowing – if not and the injectors are opening then there’s a problem with the pump or the filter or even the pressure regulator

Could also be incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will never add the 'cold start' extra fuel required if the car starts OK when warm then I 'd look into changing the sensor.

My goal is to give you the best advice that I can and I hope that I've helped today. Please remember to rate my service by selecting from the 5 stars at the top of the screen before you leave. If you need more help, use the reply box to let me know.

If you're not pleased, also let me know because rating bad does not result in a refund, there are better options. Rating now will not close this post nor prevent further replies

Thanks Matt

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Customer reply replied 4 months ago
Its has a carburetor and is getting fuel and try to start then there is nothing just turning over try to bump start would not work either
Jeep Mechanic: Matt, Engineer replied 4 months ago

OK

thanks for letting me know about the carb

so this does simplify things a little

I'd still start by checking for spark as I've described and if its not there then check that there's 12V at the coil with the ignition on and if thats OK then pull the distributor cap off and check inside for damage to the posts and the rotor arm

then check to see if the speed sensor /pickup inside the cap has the correct gap ( usually 1.5 to 2 thou) and measure the resistance of the pickup as its should be at least 200 ohms

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Jeep Mechanic: Matt, Engineer replied 4 months ago

Hi
do you still need help?
Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! If you're not pleased, also let me know because rating bad does not result in a refund, there are better options. Rating now will not close this post nor prevent further replies
Thanks Matt

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Matt
Matt
Matt, Engineer
Category: Jeep
Satisfied Customers: 22,932
22,932 Satisfied Customers
Experience: Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.

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