2001 GMC Jimmy 4.3, No Power on Acceleration, Fuel Delivery Problem

(This is not the actual vehicle we worked on. We did not get a picture of it, so we are just showing a comparable one. The one pictured is a 1999 GMC Jimmy from http://www.edmunds.com/gmc/jimmy/1999/.)

***This entry will not be so much a "how-to" as it will be a teaching point about testing a fuel pump's circuits before removing it from the tank. Therefore, there will not be as many pics in this post. We will simply discuss what we did and then focus on the test, with a couple of pics to go with it.***

This vehicle came into the shop with a customer concern of no power on acceleration. The customer described the symptoms as bogging when pressing the accelerator. The customer believed the fuel filter could have been the issue.

We drove the vehicle and verified the customer's concern. There was a definite issue with fuel delivery. We checked the readings on the Scan data and found the O2 sensors were reading lean at WOT (i.e. Wide Open Throttle). At WOT, with proper fuel pressure and volume, the O2 sensors should peg out Rich. In this case, they did the opposite, they dropped to 0mv, indicating a fuel delivery issue.

We put a fuel gauge on the vehicle and got a reading of around 50psi. This vehicle's spec is 60psi and up.

We removed the fuel filter first and sure enough, it was completely clogged. Per the customer's request, we changed the filter first and test drove the vehicle again. As we assumed, the vehicle had the same symptoms.

It was now time to drop the tank and take a look at the fuel pump. The filter was an obvious issue. It was stopped up due to a lack of proper maintenance.

The pump probably failed because of the poor shape of the filter. The pump had to pump against that resistance and simply wore out because of it.

One mistake that we have seen committed over and over, is having a faulty fuel pump and then simply jerking it out and putting a new one in the vehicle. There is a simple test that needs to be performed before removing the old pump.

That test is called a voltage drop test. Basically, with this test, the tech is testing the power side circuit and the ground side circuit to make sure everything is good. A problem with either of these circuits can cause the same symptoms a bad pump will display.

If there is a problem in one of the circuits, even though the pump probably will need to be replaced, if the tech simply puts a new pump in the vehicle, it will not be long until that pump is faulty too.

We have seen, and heard, of many such cases where a pump is replaced, only to have the new pump go out within a few weeks or months of installation. The issue, almost every time, was not a faulty new pump (though that does happen); but rather, an issue with the circuitry.

The issue is that resistance builds up in one side of the circuit or other and causes the pump to fail prematurely. If the test is done and too much resistance is found, the tech then has to divide the circuit and start searching for the problem area.

We won't give a detailed definition here of voltage drop, it can be found easily online.

Before removing the original pump, here is the test we performed to check the voltage drop. The picture below is where we back probed at the fuel pump electrical connector.

We took a DVOM meter and connected one end to the battery and  the other to the fuel pump electrical connector. We tested the power side first and then the ground side.

What we were looking for is a reading under about .5v or 500mv. As long as the reading is below half a volt, the circuit is good and the pump can be replaced with no worries. (The test must be performed with the pump running.)

First we test the power side. In the picture below you will see the reading is well below 500mv.

This test told us our power feed was good. We then moved to the ground side. As you see in the picture below, it too was below the 500mv threshold.

This test took 5-10 minutes. In that short time, we tested and found the power feed and the ground circuits to be in good electrical shape.

We were then confident to R&R the original pump, retest the pressure, take it for a test drive and ship it to the customer.

Taking the time to do the little things right, will help to prevent costly and unwanted returns. It makes the tech's life simpler and happier and the customer's too!

2006 GMC Sierra, 5.3, 4WD, Rear Brake Shoes (Single Spring Application)

This 2006 GMC Sierra 5.3, 4WD, came into the shop for its 100,000 mile maintenance. We replaced the spark plugs, wires and air cleaner element. We also added oil to the front and rear differentials.

Another service we performed was an all-around brake job. We replaced the front brake pads and the rear brake shoes. We also had the front rotors and rear drums resurfaced at a machine shop.

In this post, I will concentrate on the rear brake shoes. These have a single spring application. They are known to be a bit of a problem. Many techs and DIYers complain about this setup. I will show you a few things I have learned from doing them.

In the two pictures below, you will see the single spring. It looks something like a horseshoe and has a lot of pressure on it. They do make a special tool just for pulling this spring back and removing the brake shoes. I did not use the tool on this job. It is possible to do the job without the expense of the special tool. However, caution is advised, as the spring is very tight.

In the picture below, you will see one of the brake shoes. On this application, the whole apparatus is replaced. When you purchase the new brake shoes, it will come with the shoe and the parking brake lever attached. All of it comes off and is replaced, unlike on other applications where you simply remove a keeper and the parking brake lever remains on the vehicle. 

Removing the cable from inside the spring going to the parking brake lever can be troublesome. In the picture below, you will see the new brake shoe (parking brake lever and spring conduit attached). The parking brake cable goes through the spring conduit and hooks to the parking brake lever. Again, this is the part that many people find very frustrating.

To make this much easier here is what I do: first, (on this model with extended cab), I look below the back of the extended cab on the frame. In that area is the connector for the front cable coming from the parking brake to the two rear cables each going to one side respectively. Below you will see the area and then a picture of the connector on the frame:

Once the connector is located, I detach one (or you can do both at the same time) of the rear cables. See the picture below:

I can actually detach it just using my hands, so it is not that hard to do. I believe the top cable goes to the right (passenger) side and the bottom one goes to the left (driver) side. Once the rear cable is detached from the connector, I now have slack on the other end (the brake shoe end) to move the cable in and out easier. See the picture below:

There is a tab on the end of the spring conduit that must be pressed down to allow the cable to slip out of the spring. Sometimes the cable will come out of its own accord once I detach the connector. Now the brake shoe (with parking brake lever) will slide right off the parking brake cable. See the pictures below:

To remove the shoes themselves (without the special tool) I simply use a large screwdriver, pliers and a pair of side-cutters. There is an adjusting spring to remove, along with the adjuster.

I always grease the contact points to make for a nice, smooth and quiet braking experience. I use caliper grease on the rear brakes and front as well. See the picture below:

I also make sure to clean up all hardware with a good quality brake cleaner.

Once the job is done, I always torque the lug nuts to specification.

I torqued all four wheels to spec and then test drove the vehicle. All was well. The brakes felt good and smooth and the parking brake worked smoothly as well. We shipped this one to the customer. Another one fixed.

2008 Ford Mustang 4.0, Coolant Leak at Thermostat Housing

This 2008 Ford Mustang 4.0 came into the shop with a complaint of a coolant leak. The customer had taken it to a Quick Lube for an oil change and they had advised him he was leaking coolant. Upon inspection, we determined the leak was coming from the lower thermostat housing (which is plastic). This is a very common problem on these and other Ford vehicles. We have replaced quite a few.

Below is a look under the hood. First, we must remove the air duct.

In the below picture, you will see the air duct has been removed.

The next step is to remove the throttle body chamber. There are four bolts (8 mm heads on them) and two electrical connectors. Below is a picture of the TB removed. We also removed the upper radiator hose from the upper thermostat housing.

The next step is to remove the three bolts holding the upper thermostat housing in place. We removed these bolts, the upper housing and the thermostat and gasket from the lower housing: see the picture below.

Now, the lower thermostat housing is readily visible. There are three bolts that secure it to the intake manifold. These three bolts must be removed, along with two hoses and an electrical connector. Once these are removed, the lower housing can be tilted and removed from the vehicle: see picture below.

Below are pictures of the removed lower thermostat housing. You can see it was leaking at the seam. This seam, however, is not repairable and the whole lower housing must be replaced.

Below is a picture of the engine with the lower housing removed and the area cleaned.

Below is a picture of all the parts needed to finish the repair. Everything is OE from Ford. We replaced the lower housing, the thermostat and three O-rings:

The lower thermostat housing:

The thermostat and three o-rings.

Below is a picture of the new lower housing:

Simply reverse the steps to install the new part. Be sure to torque the bolts to specifications. Remember, this housing is plastic and could easily crack if over-tightened. 

We finished putting everything back together, filled the tank with coolant, started the engine and checked to make sure the coolant was full. Drove it down the road, let it idle in the bay and verified the leak was now gone. We shipped it to the customer. Another vehicle repaired and out the door.

2001 PT Cruiser, Blower Fan Not Blowing as Much Air as Normal

This 2001 Chrysler PT Cruiser came into the shop with a customer concern that the AC/Heater Fan was not blowing as much air as it usually did. The customer commented that she had tried the fan at different speeds, and while the fan would work at every speed, it just did not feel as if it was blowing as hard as it once did.

As we inspected the vehicle, we found the problem was not with the fan or its circuits; but rather, with an unwelcome guest!

In this post, I will not show so much how to do the job, as I will what we found and where. If you have one of these vehicles and experience the same sort of concerns this customer had (i.e. blower fan works at all speeds, but does not blow as much air as normal) then you may have the same culprit.

To get to the problem, you will have to remove the vent cover over the windshield wiper fluid reservoir.

Once it is removed, you will see the reservoir.

There are a couple of bolts holding the reservoir in place. You will need to remove them, so that you can position the reservoir out of the way.

Once it is out of the way, you will find a rodent has been setting up shop in the air duct passage. You may find, as I did on this vehicle, strips of paper all matted together, or leaves and sticks. You must remove this foreign object from the passageway.

As you can see from the above picture, it is quite a bit of stuff blocking the airflow for the blower fan.

Above you will see the mass on the floor of the shop. Needless to say, once this had been removed from the passageway, the fan blew nice and strong once again!

We put everything back together and shipped the car. Another satisfied and cool customer!

2007 Suzuki Forenza 2.0, Rough Running Engine and Overheating Issues

This 2007 Suzuki Forenza with a 2.0 came into the shop a couple of months ago with a customer concern of a rough running engine and an overheating issue. We felt pretty confident we were looking at a blown cylinder head gasket at this point; but, we wanted to "test and not guess".

There are a couple of ways to check for a blown cylinder head gasket. One way is to pressurize the coolant system and, with the spark plug out of the missing cylinder (or all plugs removed), using a bore scope in the cylinders to check for seeping coolant. Another way is to use a 5-Gas Analyzer to check for combustion gases in the coolant system. The third option, similar to the second, is to do what is called a block test.

We opted for the third option. It is a method we have used often with great success.

Before this, however, we wanted to perform a visual inspection.

When the customer drove the vehicle up to the shop, we noticed the tell-tale white smoke out the tail pipe. It was quite pronounced and the smell of coolant in the exhaust was noticeable.

The next visual inspection was of the oil. As you can see in the pictures below, the milky look to the oil is a sure sign that coolant has entered the crankcase.

We let the vehicle sit and then took the cap off the coolant tank. We noticed when we started it, fumes coming out of the tank.

Per the instructions with the block test kit, we let the vehicle run for about ten minutes and then performed the test. The kit comes with a clear tube and a fluid. The fluid is added to the tube, then you place the tube over the coolant tank opening. You apply vacuum to the top of the tube, in this case we used a hand-held vacuum pump, and apply vacuum for a minute or two. If combustion gases are present in the coolant, which they should not be, then it confirms a problem. (If there is a problem, the fluid, which is blue out of the bottle, will turn green.) Of course, it could be a blown head gasket, a cracked head . . . etc., but you confirm there is a problem that calls for a top-end engine tear down.

In the picture below, you see the fluid just added to the tube. You can see it is a light blue color out of the bottle. If the test passes (meaning no combustion gases are detected in the coolant system; hence, no blown head gasket) the fluid will remain blue. However, if the test fails, (combustion gases detected) then it will turn green within a minute or two.

Here I am showing (minus the fluid) how the tube fits on the coolant tank. (It is minus fluid because I just took the picture to demonstrate how to do it.)

As I applied vacuum (via the vacuum pump) to the top of the tube, within seconds, the blue fluid changed to green. This confirmed a failure at the mating of the head and block. Now, it was time to remove the head, send it to the machine shop and replace the head gasket.

We replaced the head gasket, timing belt and water pump and other odds and ends. Put it all back together and the vehicle ran nice and smooth. We test drove it a few miles and shipped it to the customer.