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Greg
Greg, import technician
Category: Mazda
Satisfied Customers: 7053
Experience:  17 years shop owner import
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2007 mazda cx7 replaced engine w short block utlized all old

Customer Question

2007 mazda cx7 replaced engine w short block utlized all old components will crank but not fire
Submitted: 1 year ago.
Category: Mazda
Expert:  Greg replied 1 year ago.

Hi .

Have you checked what is missing .Spark ,fuel etc..

Spray ether down the throttle body when cranking over the engine .

Did you use new spark plugs .

What problem did you have with the old engine .

Rgds Greg

Customer: replied 1 year ago.
the old engine threw the timing chain. It was repaired and ran for a year. Then one of the pistons either came loose or broke and hit the head.
Customer: replied 1 year ago.
i have not tried the ether. figured there may be something keeping the motor from firing like a sensor. The short block was supposed timed before shipment. the camshaft timing was not set by the engine installer.
Expert:  Greg replied 1 year ago.

You use your head on this new block or did the block come with a new head also .

Customer: replied 1 year ago.
new head
Expert:  Greg replied 1 year ago.

Came complete with timing chain set up .

or did you have to fit the timing chain .

Greg

Customer: replied 1 year ago.
had new timing chain and camshafts already timed according to AAA engines where I purchased it. Making sure installer did not mess up the timing while working on it. also trying to determine if he installed new plugs.
Expert:  Greg replied 1 year ago.

When checking the plugs do a compression test .

If it came complete i'n sure the timing chain is correct .but a compression test will confirm this .

Greg

Customer: replied 1 year ago.
cant run compression test until this weekend....will advise then....
Customer: replied 1 year ago.
also checking the fuel injector and ignition circuits with a Noid Tester....if possible.
Expert:  Greg replied 1 year ago.

Yes injector circuit you can check with a noid light ..

Coils you just need to check that all are sparking at the plugs ,

Greg

Customer: replied 1 year ago.
No fire
Compression 1 153 2 123 3 153 4 165
Customer: replied 1 year ago.
All fuses ok
Expert:  Greg replied 1 year ago.

Looking at the compression looks like the timing is off .

Do a wet compression test, if it comes up to 180 its rings, stays low timing off or valve not sealing,

then to check if timing or valve put each cylinder at TDC (valve rockers lose) and do a leak down test ,this will confirm valves . .

For a new block and head, compression is like an engine with 400.000 miles bad.

I would get in contact with the engine supplier and give them the compression readings

as said a good engine will have 180 psi even on all cylinders .

Rgds Greg

Expert:  Greg replied 1 year ago.

Just checking in to see if you still need assistance with this issue .

Kind regards Greg

Customer: replied 1 year ago.
Ok any obvious reason there is no fire
Expert:  Greg replied 1 year ago.

Check for malfunction codes .

Could be a cam / crank sensor ??

But check for any new codes .

Crank engine\ for 10 seconds does the Rev counter show 250 rpm +/-50 rpm .

Greg

Customer: replied 1 year ago.
In order
P2088 p0091 p0443
P0403 p2009 p0091
Expert:  Greg replied 1 year ago.

Okay these are all engine wiring harness connection codes .OCV, Fuel pressure regulator ,EVAP purge control valve ,

variable swirl solenoid circuit ,

All low circuit which means the wiring harness has a bad connection ,bad ground connection ,

short to ground ,Possible PCM malfunction, check all connections you had apart for the engine swap.

Do these checks then get back to me .

Greg

Customer: replied 1 year ago.
checked most of the connections but not all. Still working on them. Is there any type of vehicle immobilization that needs to be reset.
The RPMs while cranking are ok, its turning over fast, but doesn't register on the engine code device???
Expert:  Greg replied 1 year ago.

The RPM is not showing on the scan Tool in live data ,if not its the wiring harness as said or the Crank shaft sensor

Customer: replied 1 year ago.
I checked the continuity of wiring harness at crankshaft sensor term A to Pcm and it shows open. B has continuity to its correct pin plus about 6 other pins??? And c is open back to term E on main engine relay
Expert:  Greg replied 1 year ago.

If you are not getting a reading to the PCM then you need to correct the wires with the open which means there is a break in the wire .

Fix these two lines then the PCM should see the signal from the sensor .

Rgds Greg

Customer: replied 1 year ago.
Is there a part number for the complete wiring harness. I think I should just replace the complete item
Expert:  Greg replied 1 year ago.

Engine wiring harness .

To make sure you get tthe right part i suggest you go OE Mazda at the dealership ..

Rgds Greg

Customer: replied 1 year ago.
I replaced the wiring harness that goes from the sensor all the way to the lower PCM (2). No change. There still is no reading on my scan tool. I checked the crankshaft sensor and it isn't giving a pulse on the voltmeter in the VAC mode (2V). The ohm readings on the probe are 1800 ohms. While the probe harness was removed I checked the continuity of each pin. The C pin doesn't show continuity to the E port of the main relay, but shows continuity to the battery ground. This is the same thing I am seeing at the camshaft sensor A pin. When checking the APP sensor I am getting 2.5 V and 3.5V on each wire no matter if the pedal is depressed or not, no change. Have yet to check the MAF sensor. Note on the ladder diagram these are all on the b circuit, which means they are connected to the main relay E port.
I removed the breaker/fuse box cover to see if there were any wires shorted or grounded and didn't find anything.
Plan is to purchase a new crankshaft and camshaft sensor and replace the main relay and the coils on spark plugs. Not sure how to better test the APP sensor because I cant find it.
Is there anyway to test to see if the correct voltage is going to the coil packs?
Customer: replied 1 year ago.
any idea?
Expert:  Greg replied 1 year ago.

Going to reopen this for our auto electric techs .

Rgds Greg

Customer: replied 1 year ago.
Never heard back! I've replaced several sensors and one coil pack.
Still no luck firing. I randomly decided to check continuity between battery leads. I m getting 600 ohms. Does this tell you anything? Seems like it should be infinite.
Customer: replied 1 year ago.
Now I put it all back together and it has a signal showing rpm and it fires just for a second but won't start.
Customer: replied 1 year ago.
It tries but only initially fires. I sprayed ether and tried it and it backfired really loud once. Also fuel press is only about 70 psi w spikes to 90 occasionally . Spill back solenoid will pull in and I'm getting 9.7 v to it. Resistor is .4 ohms on a 200 ohm range. All relay and fuses check ok.
Customer: replied 1 year ago.
Still no response from anyone....
I checked the injectors the resistance is in spec. The FRP sensor is getting 5 volts, and has resistance of 700 ohms on two different pins. Spill back solenoid is moving about 1/8" at the plugger. I still only get on rotation of firing then it will not fire again until the ignition is turned off and back on. There are no codes showing at this time.

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