1988 E350 Class C 460 EFI Won't Start - Advanced Fix

The Straight Answer

Looking at your 1988 E350 Class C with what you describe as a 460 EFI (note: most 1988 460s came with carburetors, but some late 1988 models may have had EFI), you've done incredible diagnostic work already, but I suspect you're dealing with either a failed ECM (Engine Control Module) or a major wiring harness issue between the ECM and engine sensors. The fact that it won't even fire with ether is the key clue here - since ether should fire even with marginal ignition, this points to a significant ignition timing or control issue and points to either complete loss of ignition timing control or ECM failure. Given that you've verified spark and timing mechanically, but the engine won't respond to ether, the ECM is likely not commanding proper fuel injector pulse width or ignition timing advance, even though you're seeing spark at the plugs.

Your 460 EFI system relies heavily on the ECM to coordinate fuel injection timing, ignition timing, and injector pulse width based on sensor inputs. Since you've replaced the major ignition components and verified fuel pressure, the ECM is the brain that ties it all together. The symptoms you're describing - occasional attempts to "hit" but never actually running - suggest the ECM is intermittently trying to fire the injectors but failing to maintain consistent control. Common causes of this include ECM capacitors failing after 35+ years on these older Ford EFI systems.

Breaking It Down

Let's walk through what's happening with your 460 EFI system. Ford's Electronic Fuel Injection on the 460 was relatively new technology in 1988, and these systems have some known weak points that become more apparent as they age. The EEC-IV module in your rig is typically located on the firewall or in the engine bay, and it's responsible for reading inputs from multiple sensors including the MAF (Mass Air Flow), TPS (Throttle Position Sensor), coolant temperature sensor, and oxygen sensors, then commanding the appropriate fuel delivery and ignition timing.

The fact that you're getting fuel rail pressure within manufacturer specifications confirms your fuel delivery system is working correctly. Your replacement of both high and low pressure pumps was thorough, and the inertia switch replacement was smart thinking. The TFI module and distributor replacement should have addressed ignition delivery issues, but here's where it gets tricky with EFI systems.

Even though you're seeing spark, the ECM controls the exact timing of that spark through the TFI module. If the ECM isn't functioning properly, it might be providing spark, but at completely wrong timing intervals. Similarly, even with good fuel pressure, the ECM controls when and how long the fuel injectors stay open. A failing ECM might not be sending proper pulse width signals to the injectors, meaning they're either not opening at all, opening for too short a duration, or opening at the wrong time in the engine cycle.

The ether test is particularly telling. Ether should fire even with marginal ignition systems because it's so volatile. The fact that it won't even pop on ether suggests either the ignition timing is so far off that it's not occurring anywhere near the compression stroke, or the ECM has failed to the point where it's not providing consistent ignition commands. Another possibility is that one or more critical sensors are sending completely erroneous signals to the ECM, causing it to go into a "limp mode" where it won't allow the engine to run.

What You Need

To properly diagnose this ECM issue, you'll need some specialized tools and parts. First, you'll need access to a Ford-compatible EEC-IV diagnostic tool or code reader. The 1988 system uses EEC-IV diagnostic protocol, which is different from modern OBD-II, so a standard code reader won't work. You can often borrow these from auto parts stores, or you can access the codes manually using the diagnostic connector and counting the check engine light flashes.

For testing ECM power and ground circuits, you'll need a digital multimeter with the ability to check for voltage drop across circuits under load. The ECM requires clean 12V power and multiple good ground circuits to function properly. Even though you've checked some grounds, the ECM has several ground paths that all need to be verified.

If the ECM testing points to replacement, you have several options. A remanufactured EEC-IV module for your 460 EFI will run between $200-400. The correct module for your model should be verified by part number, as specifications vary by engine configuration and build date.

You'll also want to have on hand electrical contact cleaner and some dielectric grease. The ECM connector can develop corrosion issues that cause intermittent failures, and cleaning these connections is often part of the solution. Additionally, pick up a tube of conductive grease for any ground connections you disturb during testing.

Doing the Work

WARNING: Before beginning any ECM diagnostics, disconnect the negative battery cable and wait at least 10 minutes. ECMs are sensitive to voltage spikes and static electricity. Use proper anti-static procedures and avoid disconnecting ECM connectors with the battery connected, as this can damage the module.

Start your ECM diagnosis by pulling diagnostic trouble codes from the system using EEC-IV procedures. On your 1988 system, locate the diagnostic connector under the hood. Perform KOEO (Key On Engine Off) test by turning ignition to "run" without starting and observe check engine light flash patterns. Since your engine won't start, you'll only be able to perform the KOEO test initially. Each code will flash as a series of pauses and flashes - write them all down.

Common codes that point to ECM failure include codes related to multiple sensor circuits failing simultaneously, or codes indicating the ECM can't communicate with various components. If you're getting no codes at all, or if the check engine light doesn't illuminate during the test procedure, that's often a sign of ECM failure itself.

Next, test the ECM power supply circuits. The ECM needs constant 12V power from the battery, switched 12V power from the ignition, and multiple good grounds. Use your multimeter to verify you have clean 12V at the ECM connector with the key on. Check for voltage drop by measuring between the positive battery terminal and the ECM power pin - you shouldn't see more than 0.1V drop. Do the same test for the ground circuits between the ECM ground pins and the negative battery terminal.

If power and ground check out, the next step is testing sensor inputs to the ECM. Start with the MAF sensor, which is critical for proper fuel delivery. With the ignition on but engine not running, the MAF should show values within manufacturer specifications (verify with service manual). The TPS should show approximately 0.5V at idle position and sweep smoothly to around 4.5V at wide open throttle. The coolant temperature sensor should show appropriate resistance values for ambient temperature.

Here's a critical test many people miss: check the ECM's ability to command the fuel injectors. You can do this by using a "noid light" tester plugged into each injector connector while cranking the engine. These lights flash when the ECM sends power to the injector. If you're not seeing any noid light activity, or if the pattern is erratic, the ECM isn't properly commanding fuel delivery.

SAFETY WARNING: When working around the fuel system during injector testing, ensure adequate ventilation and have a fire extinguisher nearby. Fuel vapors can ignite from electrical sparks.

If all your tests point to EEC-IV module failure, removal and replacement is relatively straightforward but requires care. Consult your service manual for specific removal and installation procedures for your model. Disconnect the battery before unplugging the ECM connectors to prevent damage to the replacement module.or, and be careful not to bend any pins. When installing a replacement ECM, apply a thin coat of dielectric grease to the connector pins to prevent future corrosion.

Time for a Pro

While ECM diagnosis and replacement is within the scope of a dedicated DIYer, there are several scenarios where professional help becomes necessary. If you're not comfortable working with electrical diagnostics, or if you don't have access to the proper diagnostic equipment, a shop specializing in older Ford fuel injection systems can save you significant time and frustration.

Professional diagnosis becomes particularly valuable if your initial ECM replacement doesn't solve the problem. Sometimes what appears to be ECM failure is actually caused by a failing sensor sending bad data to a good ECM, causing it to go into protection mode. A good technician with Ford factory scan tools can monitor ECM inputs and outputs in real-time to pinpoint exactly where the communication breakdown is occurring.

Additionally, if your diagnostic trouble codes point to multiple circuit failures, you might be dealing with a main wiring harness issue rather than ECM failure. The engine harness on these rigs runs through some harsh environments and can develop multiple failures over time. Professional shops have the experience to quickly identify harness problems and the tools to repair them properly.

The cost for professional diagnosis typically runs $100-150 per hour, and most shops can pinpoint ECM-related issues within 1-2 hours. If harness repair is needed, expect additional costs of $200-500 depending on the extent of the damage. However, this investment often pays for itself by avoiding the trial-and-error parts replacement that can quickly exceed professional repair costs.

One final consideration: if your ECM replacement solves the immediate problem, consider having the shop check the charging system voltage regulation. ECMs can fail prematurely if they're subjected to voltage spikes from a failing alternator or voltage regulator. A simple charging system test can prevent you from burning up your new ECM and getting stranded again on your next camping trip.