Troubleshooting The Fuel Pump (GM 4.3L, 5.0L, 5.7L)

In this article, I'm gonna' evidence you the most effective way to examination the fuel pump on GM iv.3L, v.0L, 5.7L engines with the 'Spider' fuel injector assembly and information technology involves using a fuel pressure gauge. I've also included how to check a no fuel condition with starting fluid (although this is not the most effective way to test the fuel pump).

It's been my experience that misdiagnosing a bad fuel pump is a mutual occurrence on the 4.3L, 5.0L, 5.7L GM vehicles with the 'Spider' fuel injector associates. Why? This is because in about fifty% of the time, the fuel pump delivers enough fuel to keep the engine running but not enough to offset the engine (instead of just frying completely and not delivering any fuel at all). When this happens, you're able to spray starting fluid (or carb spray) downwardly the engine and it'll showtime and run (in one case you turn it off, you lot have to spray again to get it started).

Yes, allow me repeat that one more fourth dimension: As crazy as this sounds, the fuel pump volition deliver enough fuel to proceed the engine running, but not enough to showtime it when you're cranking the engine and this makes a lot of folks call back that the problem lies anywhere else but in the fuel pump!

NOTE: This tutorial merely covers GM pickups and SUVs equipped with the 'Spider' fuel injection system. For the fuel pump test of throttle trunk fuel-injected (TBI) pickups and SUVs, the post-obit tutorial will aid:

  1. How To Exam The Fuel Pump On GM TBI Fuel Systems.

Of import: Since you'll be working effectually gasoline and/or starting fluid, be careful, take all necessary safe precautions and recollect safety all of the time.

En Español You can discover this tutorial in Castilian hither: Cómo Probar La Bomba de Combustible (GM 4.3L, 5.0L, 5.7L) (at: autotecnico-online.com).

Which And Where To Buy A Fuel Pressure level Estimate

Troubleshooting The Fuel Pump (GM 4.3L, 5.0L, 5.7L)

Owning a fuel force per unit area gauge is now condign a must. All vehicles now utilise an electrical fuel pump to deliver fuel (under high pressure level) to the fuel injectors and the best way to diagnose this fuel pump is with a fuel pressure level approximate.

In all of the GM iv.3L, 5.0L, 5.7L equipped vehicles, GM was kind enough to put a Schrader valve on the fuel injector rail where yous can tap into the fuel arrangement and cheque its performance.

A fuel pressure judge tin cost you as little as $40 (US) or equally much as $200 (US). The price departure depends on what blazon of fuel force per unit area gauge set yous buy, this means either buying a not-professional technician grade tool or a professional technician form tool. Whichever 1 you buy, it's an investment that volition pay for itself many times over.

I'm going to review two different fuel force per unit area gauge sets that will shed some light into which one is the ane yous may want/need to buy.

Your local Parts Firm will have a fuel pressure estimate set to sell you, although you'll pay more for it and it won't be a professional course tool (if that's what you're looking for).

The ones I recommend are either the Actron CP7838 Professional person Fuel Pressure level Tester or the OTC 6550 Primary Fuel Injection Kit. In the next paragraphs I'll explain why.

The Actron CP7838 Professional Fuel Pressure Tester is a good tool but not a professional technician level fuel pressure judge. Although the name used past Actron to depict information technology has the discussion 'professional' as part of its name.

Why do I know this is a good tool? Well, I own i (I likewise have a professional level grade fuel pressure gauge prepare) and I accept used it in a regular manner and I can tell you that it works.

The simply things I don't like almost information technology is 1.) No molded case to put the fuel pressure level estimate and the fittings that go with information technology and 2.) Yous can't purchase the fittings, that you may lose or break, separately. But for the price, it's a great deal.

You'll be able to test almost of the GM vehicles, most Ford vehicles, amidst several makes. Although this is not that important if you're but worried about testing your GM vehicle.

The OTC 6550 Master Fuel Injection Kit will have the adaptors for Asian and Domestic (USA) vehicles. So, if you work on cars for a living and you work on a diversity of Makes and Models, this is the fuel pressure estimate set that you need to have in your tool box.

Since this fuel pressure gauge set is a professional course technician tool, you tin can buy most of the components, that make up the set up, separately. This comes in handy, because you're able to purchase whatever fitting you lose or gets damaged.

Likewise, and probably the last consideration, is that this is an OTC tool, and OTC has been around for a long, long time and makes a ton of automotive specialty tools known for quality.

TEST ane: Checking The Fuel Pressure Specification

Troubleshooting The Fuel Pump (GM 4.3L, 5.0L, 5.7L)

The fuel system in your 4.3L, 5.0L, or 5.7L Vortec engine needs at least 50 PSI of fuel pressure to start.

The fuel pump produces much more than just 50 PSI of course but the bare minimum the engine needs to showtime is 50 PSI. Annihilation less and it will crank for always before it starts or non commencement at all.

So, the very first thing you demand to do is to verify that the fuel pump is delivering at to the lowest degree 50 PSI of fuel pressure while the engine is cranking. Aye, while the engine is cranking.

Locate the Schrader valve on the fuel line that connects to the 'Spider' associates. This is where you'll connect your fuel pressure approximate (the first photograph, in the paradigm viewer, is of a 4.3L, and the second of the V8 engine).

Annotation: In case you're wondering, the factory manual specifies that the fuel pressure level for the CSFI system should be between 56-62 PSI. The CPI system's fuel pressure should exist between 60-66 PSI. The manual doesn't specify if this pressure is key on engine off, only that this pressure should be maintained 'under all operating conditions'.

If you don't know whether you accept a CPI or CSFI system, you can detect out the difference between them past checking out the info in this subheading: 'Spider Fuel Injection Nuts' found in this tutorial: How To Test The 'Spider' Fuel Injector Associates (iv.3L, 5.0L, 5.7L).

OK, to get this testify on the road, this is what yous'll demand to do:

  1. 1

    Connect your fuel pressure estimate to the Schrader valve.

    Before you install the fuel pressure gauge, identify some rags around information technology and underneath the fuel line (in case some fuel spills out when y'all connect the guess to information technology).

  2. 2

    Pressurize the fuel organization by activating the fuel pump.

    You tin can do this by simply turning the key ON and OFF several times. Once the fuel pressure gauge registers pressure, check for fuel leaks around the Schrader valve.

    Information technology's very important that NO fuel leaks are present for the accuracy of the test. Once you accept verified no fuel leaks, go along to the next step.

  3. 3

    Accept your banana crank the engine as you eyeball the fuel pressure gauge. Information technology'due south important that you have someone else creepo the vehicle so that you lot can eye-ball the fuel pressure gauge.

  4. 4

    Y'all'll go one of two results with this examination:

    1.) The fuel pressure gauge will register at least 50 PSI and the engine will first or.

    2.) The fuel pressure level gauge will register 49 PSI or less and the engine will Not Starting time.

OK, allow's detect out what your fuel pressure gauge results hateful:

CASE 1: If your fuel pressure guess read 50 PSI or more as the engine cranked. This means that the fuel pump on your 4.3L, v.0L, or 5.7L is OK and not the cause of your no-start condition.

The side by side step is to observe the fuel pressure gauge's needle (after your helper stopped cranking the engine). The needle should descend to nearly 40 to 45 PSI and stay there for at least 4 to v minutes. If the needle DOES Non stay at this fuel pressure level (more specifically: if the needle drops to 0 PSI immediately -by immediately I mean within the first 15 seconds), you have either the fuel pressure regulator or a fuel injector leaking fuel inside the plastic intake plenum.

You lot can find the fuel force per unit area regulator exam here: How To Test The 'Spider' Fuel Injector Assembly (iv.3L, 5.0L, 5.7L).

Important: This test result could be telling you that the PassLock anti-theft system has armed itself and is keeping your pick-up or SUV from starting. I recommend taking a expect at the post-obit section (in the next page): Difference Between A Bad Fuel Pump And An Anti-Theft System (PassLock) Failure.

The following tutorial may besides be a expert starting point in diagnosing the cranks only does non commencement status your GM pickup or SUV is experiencing (if it's not fuel pump related): How To Troubleshoot A No Start (GM 4.3L, 5.0L, 5.7L).

CASE ii: If your fuel pressure gauge DID Not read 50 PSI or more equally the engine cranked. This ways that the fuel pump is bad, even if you spray starting fluid down the throttle body and your vehicle Starts.

If the engine does not get at least 50 PSI when cranking, it won't commencement (and is the surest indicator that the fuel pump will go completely bad in short). If in your case the gauge read 45 to 49 PSI, the engine will eventually kickoff after several attempts equally the fuel starts to accumulate on the Pistons or if you spray starting fluid (or carb spray) into the intake.

If the fuel pressure level reading was 0 PSI, then the fuel pump is probably fried. Why 'probably'? Well, yous still need to brand sure: i.) That the fuel pump fuse and relay are OK. 2.) That you have enough fuel in the tank (don't laugh, it happens).